Let's see. I'm 37 years old. I love league. I'm a career gold player. I know it. The highest I've been is gold 2 100lp on this account, gold 1 100lp on my other. If the stars align, and I stop swapping roles, I can probably squeak into plat. I have a Bachelor's degree, but my last job was manual labor mill work 48 hours a week, for reasons. My car is paid off, my house, my land. I got a GF. She's married, but who cares. Still counts. I'm in shape, I work out. I could post a pic if you like.
The only reason I dont play league as much as I used to, is none of my friends like it. So, I would rather just play the games they like to have people to BS with and have fun with then play league solo. But, currently there is nothing anyone is really playing(LOR), so I've came back to league for a bit. I dont feel like Ive lost any reaction time. Hell, I think I'm even better because I just dont rage anymore. Just let the chips fall where they may. I dont think I have any more issues than I used to have, even with all the extra mobility champs. Maybe its because I've played videogames since I was 3. Started with an intellivision.
I've just came to the realization that Videogames are my favorite hobby. I'm not gonna be ashamed of it. I accept it. At various points in my life, I may have felt like I was wasting time. But, I've just accepted it at this point. This is my life, I feel like I've done pretty well, and my only regrets is not having kids yet. Now if I had kids, maybe I couldnt keep up anymore.
OP, its not your age or your job holding you down. If you dont see purpose in getting better, the game is not for you. League may be a team game, but in reality its a game about personal improvement. Getting better one game to the next. If you cant enjoy just increasing your own skill, then you are right; quit. Go play LoR, or a non-team game, because I think its teams that are dragging you down. My best buddy HATES all team games. He just cannot stand "being dragged down" by other players. I'd argue there are many a times hes the one dragging people down, but so be it.
The main way to get enjoyment out of league is focusing on self improvement. I mean just for giggles, I did the reaction time test. Average score over 5 tries: 175ms. I know its not scientifically correct, but I'm 37 years old(I'll be 38 in May). I dont know if I had much faster 10-15 years ago.