It also dependss though. Depends how much you care about it. If you don't care anymore about being good, and just care about the fun, then og course, quit. I don't get how you say "quit" and at the same time your unsure of your abilities. To quit would mean to stop trying to improve, but if you where trying to improve you would see improvement in your abilities.
So its really your choice and your the one that knows the answer.
He's saying it is everything around him that has made him doubt himself. That the fun has been sucked out of playing competitive. I also strongly disagree with the idea that when you quit playing competive you quit or somehow "care" less about playing and/or stop trying to improve. Some of the best people I know right now got better after "quiting" or never even played on a "real" team.
I'd say if anything since I quit my touch, and comfort level with the ball has increased. That said my physical level and mind for the game have decreased.
Realistically 1 out of what? 100? 1000? 10000? 100000? may actually have some level of success, that doesn't mean the rest care or love the game less. If you go to your average guitar shop you'll see people better than musicians that have made it, and many of them have never tried. Doing something for fun doesn't mean you're worse, careless, etc.
99 out of 100 new members on this site are between 13 and 20 and what to know what they have to do to go pro. Look at the older members, thats what they all said, almost none have made it (with a few exceptions who were already above average when they joined). Life moves on, dreams and goals change.
If I had a time machine I'd go back and not play my Senior year honestly, instead I'd of just started playing req league. I'd say give it a go, if the season starts and you aren't enjoying yourself walk away after the season. Really it's your choice though.