Still, that's a pessimistic view of chess. The platitude "Practice makes perfect" is stupid and inaccurate, but it fits chess much more aptly than it fits, say, playing the piano. (I speak from experience.) Chess is more mathematical and cut-and-dried than most things about which people try to use that tired phrase. In general, the saying should go, "Practice makes permanent." It's certainly more apt concerning music and sports this way.
Chess is much different. You can practice tactics, and you will in fact become better and better with practice. You can memorize openings (granted it's not the ideal way to spend the time), and as long as your memorization technique is good, you will definitely learn and memorize those openings.
If you don't want to play chess anymore, then I certainly wouldn't want to stand in your way. Your decision is respectable; not everyone has to play chess, and as drieper said, sometimes quitting is for the best. I just don't think chess is an old man's game through which one passes the time waiting to die. Personally, my chess skill has vastly improved in the time I've studied it. It's not true at all that the average player remains average. Most of the titled players are not prodigies; they just worked really hard to get really good.
Is chess a worthy contribution to humanity? Some can see that it is. The same can be said of music and sports as well. Chess players, musicians, and athletes aren't curing cancer... but that's all right. But if chess is not your way to contribute, then good luck in other pursuits.
Practice DOES make perfect, especially in piano.... I SPEAK FROM EXPERIENCE TOO!
Nowadays, People are afraid of unexpected turn of events in Chess. We are still waiting for a noticeable player like Bobby Fischer.
And, I am sure Adolf Hitler was not Bobby Fischer!!