https://tappedout.net/mtg-decks/budget-beginner-teaching-decks-1-green/
https://tappedout.net/mtg-decks/budget-beginner-teaching-decks-2-red/
^^ the two decks I used, I played green and the ai was red. Still getting the hang of this game but with over like 50k cards in the library and endless combos it's so deep. The AI is quite smart on Forge too. I've never played MTG in my life so this is all new to me.
I think there's more than 100 at the top levels of competitive play.
Yeah I might be off by a zero here. I'm just thinking if a player comes to me, says they want to play serious Modern tournaments, and wants to know what Red and Blue cards they should know, off the top of my head:
Counterspell
Murktide Regent
Spell Pierce
Force of Negation
Preordain
Subtlety
Ragavan
Lightning Bolt
Dragon's Rage Channeler
Uhh... Flame Of Anor?
That's 10 cards. There's others, but if you want a competitive Modern deck in Blue/Red the Murktide deck isn't far off from this list + lands.
Maybe the truth is somewhere in between (radical mtg centrism). There's tons of different decks on moxfield using tons of different cards, but the card pool does shrink the higher up you go, depending on the format.