My brain is not fast enough to perceive a single frame. Just not something that, after (counts it up) OVER 28 years of playing fighting games I've ever been able to do. I'm so bad at it that I'm not even sure it's a thing that's possible. Is this all just a mass delusion of the FGC that people are perceptive enough and can react quickly enough to follow stuff like that? No clue.
When I was younger, in my mid teens up through my late twenties, I would play fighting games allll the time with friends locally. I started out as just a button masher in each game and slowly learned which character(s) I liked best and how to pull off more and more of their moves and what their basic moves were like etc. I still never got to be any "good" at fighting games during that time, but because the friends I was playing with were of similar skill levels, we had a lot of really fun and cool matches. Because that's the thing about fighting games; no matter your skill level, and yes especially if you're playing against others with similar levels of skill, you can recognize when you've done something that feels comparatively skillful and enjoy that feeling .
Sadly I don't have anyone local to play fighting games with anymore... and playing online isn't an option because I can only use wifi for it and our wifi SUCKS. I still play single player stuff though, and a few years ago I actually started learning how to do some combos for the first time in my history in Skullgirls. Fighting games are just a lot of fun in my opinion if you treat them like a casual good time. I'm not super competitive so this has never been a problem for me. ...I mean, bit off topic but, my favorite deck in MTG of all time was one that made my opponent's deck(s) play better so I could easily steal cards from them to use as my own and it very rarely WON but was always super FUN) I love going into training modes and just using them as a sandbox to learn new things. It's a nice relaxing time and it actually does a pretty good job of getting my mind off of other things.
So no, if you DO have a lack of reaction and/or dexterity, it doesn't preclude participation in the genre in any way. IF you want to play casually or ESPECIALLY if you want to play competitively however, and you find yourself always struggling against opponents you're usually matched up against, it might be advisable to go looking for beginner communities or "learning" communities within the FGC so you can play with folks that are at a lower skill level and hopefully be able to not only have a lot of fun, but also get better over time, especially with your instincts (My instincts have, I think, been the only thing I've reliably improved upon during all these years of playing lol).
So yeah, I hope you can have a lot of fun with it, that is the whole point after all, just having fun ;) Anyway, have a good one pal, <3