Golf seems to be fairly similar. Lots of players spend every weekend at the range and take endless lessons and workshops, but never manage to get their handicap down to single figures.
It seems that there's a critical age when one's mind is better able to assimilate and make sense of the patterns in chess, and to memorize moves and positions. Chess requires a lot of pattern recognition and memorization, and if one does not train those early enough, it may be too late.
It would be a very interesting study to find out how many of those old, weak players actually did have a lot of exposure to and training in chess when they were young.. my bet is not a lot.
Also, I wouldn't expect to find a lot of highly achieving chess players who started playing chess later in life (let's say past their teens), no matter how brilliant and talented they are in other fields, or how well they perform on IQ tests or SATs. They'll probably be beaten by much younger players, no matter how much time and effort they put in to chess.
Learning to play chess well seems to be somewhat similar to becoming fluent in a foreign language, which children also usually excel in compared to adults.
Many amateurs never get good because they they don't practice the right things(e.g. putting and short game). Drive for show, putt for dough.
I've been labeled a genius as a kid and e.g. loved to beat the best chess computers at that time, Mephisto III on the highest level in the 80ies. I loved to play blind also, but stopped that when I couldn't get to sleep or would not stop dreaming about tricky moves. But I never had a chance against humans on lower levels.
The problem was the time constraint and nervousness. In tournaments and chess clubs deep thinking is not valued, only experience. Folks in the chess club mainly do train speed chess, and simple tournaments limit the time to 30mins.
But the good parts of my chess start when I can concentrate deeper than that, to the 2.5 hrs mark. As with playing against the computer those times. With time constraints I got nervous, didn't calculate through, took too high risks, or when playing against girls just made stupid mistakes. I usually was the last or 2nd to last in club tournaments (30min). I didn't like playing chess against humans at all, that's why I stopped playing it. And nowadays I could never beat a good chess computer. Because they are too fast and force me to play too fast also. It's not fun anymore.
But blitz tournaments are not the only, or even the most popular type of tournament. When you see someone's chess rating (ie. 1700, 2000, etc), those are ratings at slow time controls. When someone is referred to as a "grandmaster", it refers to a title that is earned at slow time controls. The world chess championship is played at slow time controls. There are blitz tournaments, but they are not as popular. Blitz is very popular in clubs, though. You're right there.
My guess is that you couldn't leverage your superior slow chess skills to blitz because you just didn't practice much blitz (ie. short time controls or fast games) on your computer, or against human players. This is understandable, and is quite common. It takes some practice to get used to playing blitz. I'd bet you would have made a fine blitz player if you'd put in some time practicing it, and your slow chess skills would have helped you in blitz, as blitz and slow chess aren't different games, but blitz relies more on intuition as opposed to deep analysis. But both blitz and slow chess require good pattern recognition and memorization, so your aptitude in the slow chess would have helped you in blitz, once you got enough practice in playing more intuitively at faster speeds.
Finally, as far as chess computer these days go: just because the computer moves fast doesn't mean you have to move fast. You can set whatever time controls you want when you play against a computer -- hours, days, weeks, or even turn the clock off altogether. On the other hand, chess computers have gotten so good these days that unless you're a world class player, you're just not going to beat them at their highest difficulty settings, no matter how much time you have (unless you cheat). They're still good to practice with, and you can still play slow chess (even correspondence chess, where you mail or email moves to each other and take a long time to reply) against humans. I think if you look, you'll find plenty of slow chess fans around the world that you can play.
>In certain areas, hours might be enough,
I learnt recently that Chess computers/programs are pre-seeded with standard moves and apparently do very badly if they're set to play without using the traditional openings. This seems to move against your analysis of what is needed to play chess well. Study of stock openings also appears to be required to perform well.
Chess is a good example. I've seen a 12 year old kid at a chess competition wipe the floor with dozens of much older players (people in their 40's, 50's, and up), who've been playing chess -- obsessively -- their whole lives.
This 12 year old kid has been playing chess for maybe 6 years (let's say 8 years maximum), but he totally crushes others who've played 40 or 50 years or more. Chess can be very addictive, and a lot of people spend virtually all their waking time playing it, for decades on end, studying, competing, yet that's not enough, and they can be easily beaten by someone much, much younger than them, who's put in only a tiny fraction of the time and effort they have.
I've also seen a 10 year old kid, who was really hyperactive and distracted when he played, always looking around him at everything but the chessboard, apparently interested in anything but chess. His mother sat next to him, and had to struggle to get his attention back to the board whenever it was his move. Yet he played at a high level against people much older than him. Again, he really couldn't have put that much time in to it, no matter how interested he was in it.. and he clearly wasn't that interested.
Chess is one of those fields where prodigies are relatively common, especially compared to fields like poetry that really do require a lot of life experience to be effective. The kids I've described are not that rare. It happens even at the highest levels, with Bobby Fischer being the archetypical example (becoming the youngest grandmaster at 15 and winning the US championship at 14). These days chess prodigies are even more common than in Fisher's time, thanks to computers and the internet. Still, whatever happens with them is not explained by the hours they put in to the game alone, as many people put in many more hours and much more effort than they do and still fail miserably.