Yes, but the abilities and item actives are all quite similar in broad categories -- dash, stun, slow, etc. Same with items -- broad categories of damage, magic, health, armor, etc.
To OP's point, you don't have to know the entire 100 hero roster and all of their abilities to have fun, just the general things they can do "Oh I just got stunned by that ability, might want to dodge next time"...
Obviously to be good you need to know them all, but not to get started and have fun at lower levels of play.
Yeah, there's some sparseness to it all that simplifies, but that's also offset by most abilities having a geometric component to how they're targeted or have area of effect.
Respectfully, OP doesn't know the game. You can indeed have fun playing casually like that, but your win rate will reflect the lack of what you don't know. You can't even see the game until you get some months under your belt, imo. Sound is another underrated aspect: you need to know exactly what spells are going off, how your allies or enemies will position them, based on nothing but hearing it and knowledge of the game.
There's no way I would have learned Dota without a friend to pull me along. It's a big problem with the genre as a whole. LoL is a bit more forgiving and ability spammy, but has all the same issues. And I say this as someone that got near the top of the 2v2 ladder in LoL beta (RIP original twitch malphite combo).
> There's no way I would have learned Dota without a friend to pull me along
But that's something that MOBAs can do that RTS games can't. Which is another reason why MOBAs ate RTSs lunch. I'm not sure why you're focusing on win rate when there are plenty of people who play MOBAs who are quite frankly garbage at the game(s).
To OP's point, you don't have to know the entire 100 hero roster and all of their abilities to have fun, just the general things they can do "Oh I just got stunned by that ability, might want to dodge next time"...
Obviously to be good you need to know them all, but not to get started and have fun at lower levels of play.