The first thing to note is that while there are probably more different decks in this format than in any other since widespread coverage made there be a global metagame, a lot of people are angry. Some of that is simple haterism - I don't think it's possible to make a Magic environment that people don't yell about how much it sucks. And quite a bit of that is simply the widespread coverage creating a global metagame. The very fact that you can netdeck a deck built by a pro in seconds means that there isn't a lot of chance that your explorations and deck brewing are going to net an improvement. It's certainly possible to make a new better deck, but chances are it will only be a few percentage points advantaged over the stock decks you face over and over again in major tournaments. Those issues are not going away.
But a big part of it is the way that most major decks win.
On the flip side, when Marvel loses the game, it often does so because it activates its Marvel, flips over six cards on the top of its deck looking for a game winning bomb or a game delaying giant spider and gets a 2/2 mana dork instead and just gets torn to pieces. Marvel is one of the big decks, but it's wildly inconsistent and it simply loses to its own combo failing to function often enough to hand out plenty of feel bads to its own side of the table.
From a game design standpoint, that's something to keep in mind. Games need to be fun when you are winning, but also fun when you are losing. There are a lot of matchups where losing isn't fun, and that's bad. Not as bad as Lantern Control, but bad.
The other issue is that the power of cards is all over the place.
Yes, some of the key roleplayer cards in most archetypes are cheap ass commons (the best card to precede a Smuggler's Copter is a Thraben Inspector from the commons box and the fastest way to Delirium trigger a Grim Flayer is with a Vessel of Nascency from the same). But enough of the haymakers are mythics and chase rares that when your opponent is drawing cards that are dramatically better quality than yours, it kinda feels like they are crushing you with their wallet. And when their deck isn't delivering the high quality cards it sure feels like their deck is screwing them. Nothing feels worse than a miss or near miss on a Vessel of Nascency except a miss or near miss on an Aetherworks Marvel. Between the high variance in card power level and the high cost of some of the premium cards, there are a lot of feel bads to go around.
The Main Decks
The four main decks are G/B Delirium, U/W Flash, G/R Marvel, and Mardu Vehicles. Of those four, the first three are all named directly or indirectly after a chase Mythic they intend to beat you to death with. Mardu Vehicles is named after the fact that it runs Vehicles, and the vehicles it runs happen to mostly be rares.
G/B Delirium
Very notably, the archetype doesn't really need Black. All the core Delirium enablers are Green cards (Traverse the Uvenwald, Grapple With the Past, Vessel of Nascency), the deck can survive without Liliana or Grim Flayer or Mindwrack Demon. You are mostly pairing with Black to get removal action, but you could plausibly do the game plan with White or Red if you wanted.
You fight Delirium by either running under them or racing them to the Titan. They have a very good midrange plan, and it'll be hard to get through with an army once they start putting up spiders.
U/W Flash
This deck is massively popular in large part because you only have to settle for bad cards if you want counterspells (counterspells in this format are generally pretty dire). Nevertheless, it often gets smacked down by other major decks in the format because its answers to Smuggler's Copter and Emrakul are both not that great and it also isn't marvelous at putting pressure on. Many pros have gone on record saying that this deck is a bad deck, but it keeps putting up wins in part because it is a big percentage of the meta and in part because the card quality level is higher than most decks in the format so you'll never find yourself with a matchup worse than "kinda bad".
Aetherworks Marvel
In a lot of ways, this deck is just G/B Delirium where the Black has been ripped out and slightly inferior Red removal put in in exchange for having Red based ramp available to get a faster Emrakul. Indeed, to bridge to the Emrakul casting plan, the deck runs the same Delirium and Giant Spiders package that the deck actually called "Delirium" runs. It does very well against Delirium because it gets to the same end game faster, and sometimes it just randomly wins on turn 4 when it gets 6 energy and a Marvel and then flips over the Promised End. I kinda suspect this deck would be better and more consistent if it got rid of the extremely swingy Energy + Marvel side package and just made itself into a more streamlined G/R ramp deck. But this is the world we live in, and in the current meta you should probably have access to Ceremonious Rejection even if you have to run it off of Aether Hubs.
Mardu Vehicles
The point here is that you have cheap creatures and cheap vehicles and you attack early and often, going under all this Eldrazi Titan and Archangel bullshit your opponents are trying to do. The most expensive card in the deck is Gideon at 4 and about half the stuff you put down is immune to sorcery speed sweepers for one reason or another.
The Rest of the Field
So because of the herd mentality of people in general and the speed of information propagation, the top decks mostly stay the top decks. Top end decks can both win and lose to one another and major tournaments mostly have good players playing polished decks. The chances of any particular deck being in the top eight is pretty low, so the top eights of major tournaments are mostly filled with decks that there a lot of copies of.
That doesn't mean that there aren't more decks to play! Far from it. One of the really neat things about this cycle is that there are a fucking lot of decks that you could put up good numbers with. Unfortunately, the fact that we mostly have one big tournament per week and net decking is so prevalent that each week you're very likely to mostly see the meta filled with the same four decks it was filled with last week.
The Inconsistent Decks
There are a number of decks that have probably been held back from dominance by the fact that they are simply inconsistent. While most decks in the format have to shoulder a bunch of cards that aren't really that great, the really inconsistent decks are using cards that are downright bad if they don't slot into their proper context. However, you could easily make the same critique of R/G Marvel, and any of these decks is just a few good draws in a row from winning a major tournament and becoming the new "it" deck.
Temur Energy
Grixis Graveyard
Metalwork Colossus
Abstractly, most of the cards you need to play in this deck are colorless, so your colored spells could be pretty much anything. Historically, people mostly play it with Blue because you get some card searching and Glint Nest Crane can also pilot copters. But I'm not actually sure that's right. In any case, the deck is tragically short of blockers if it doesn't get its colossus out, and it's only allowed to run 4 of them. So far, it seems like a deck that wins big and loses to itself often.
Control Decks
A Dedicated Control deck is very likely to be Blue. Many of the good control spells are blue, and many of the good control spells are instants. And well, the Torrential Gearhulk is totally a thing. Control decks that have put up good numbers include Jeskai Control (U/R/W), Grixis Control (U/B/W), and U/B Control.
Basically you're going to be spending most of your time drawing cards or countering your opponent's threats. Control decks don't have a lot of card slots available for win conditions. So it's best if those win conditions can be something that just ratchets into inevitability rather than something that needs a lot of board presence.
Wouldn't it be great if Control had spells that just randomly dribbled out a win condition while they were casting counters, card drawing, and kill spells every turn?
Personally I admire the beautiful simplicity of U/B Metallurgic Summonings Control.
Other Decks
There's actually plenty of room for additional decks. There are a number of archetypes that actually do just fine and don't appear in the main metagame "for no reason." Seriously, Sultai Madness, Vampire Aggro, Mardu Reanimator, Jeskai Thopters, even really weird shit like 5-color Bring To Light and Cryptolith Marrionettes do just fine in competitive scenarios when they are played and it's not actually clear why they aren't a bigger portion of the metagame.
Personally, I play...
Mardu Reanimator
Your dream draw as Mardu Reanimator involves slamming down a discard outlet on turn 2 or 3 and Refurbishing a Combustible Gearhulk on turn 4. From there you're a threat deck that never runs out of threats because you keep drawing more and recycling ones from your graveyard. So far I've crushed Control badly with this deck and mostly lost to the leanest of R/B Aggro and Mardu Vehicles. Against Delirium, and Marvel my record is good and against U/W Flash it's modestly poor. Overall, that would make this a solid choice in the overall metagame and there's no particular reason it isn't one of the bigger pie slices.
-Username17