As a 10 year old kid I learned alot about simple things like STAB, egg moves, base stats, strategies. what moves each Pokemon gets, etc through lectures and tests.
Even learning random stuff like even if a Pokemon might be weak to a certain move, it might not be the most damaging move you can use against it, or how to use some hidden combos like Defense Curl/Rollout, how to abuse your opponent when they used Hyper Beam.
I don't play competitive. Too much time for something that doesn't really look all that fun to me.
Though, personally, I never understood the appeal of playing competitive anything. (Like CoD, sports, etc)
Meh, it's part of human nature.
The strive to do better than others (with a fair footing or close as one can have) and the ability to improve at a game (call them a sport if you want to, kind of the concept of sport, competition between two or more people)
Only insecure and ignorant people try to debase someone online based on their username.
It did introduce me to actual battling strategy. Earl's Academy was great and it's a shame they haven't done something similar to it again, especially when GameFreak keeps adding hidden mechanics to moves.