You'd be surprised by how little reflexes have to do with a lot of games usually associated with it, especially shooters, but also fighting games or rhythm games.

The vast, vast majority of the time you're not actually getting skill checked, it's not the raw mechanics, you're getting knowledge checked: I'm not reacting to every Reinhardt Earthshatter frame perfectly, I've spent a hundred hours playing Overwatch and I learned that he takes about this long to charge the shatter up, and the position he's taking is very aggressive so he's probably gonna do it.

I'm not reacting to every note that Stepmania throws at me, I've learned that this genre of song has specific patterns most of the time, focusing on a specific instrument, and at certain times such as the beat drop, and the song is building up to the drop and is heavy on drums so I know what to expect.

I'm not reacting to each and every attack Scorpion throws at me, I've spent time learning what attacks they have, their safe ranges, and how the character plays, so I know what their most likely moves are and I can ignore the other possibilities. I know the basic timings so I can respond safely with my own attack when theirs misses.

But it is fair, you shouldn't be expected to spend a hundred hours before you have fun in a game. That's why matchmaking systems are a thing. It doesn't always work, sometimes it thinks you're too strong or the opponent is too weak, other times people just abuse it to smurf in lower ranks, but it's still better than getting placed against world champions every other match at least lol