Let me share my perspective about this matter, where football is considered as best sport and gives the opportunity to make money for a player then where more people will be interested in doing it. You said why India and China can't able to find 11 good players is because in India cricket is where money rains so every youngster from their childhood dream of becoming a cricketer than a football or javelin throw player but ofcourse India is also now focusing on improving their football participation by replicating something called ISL after the success of IPL (for cricket).
Every country has programs to improve its sport. Even though China failed to qualify for the 2026 World Cup, it doesn't mean they don't care about their football. It's just that Indonesia might have been luckier in the previous round, managing to beat China. As far as I know, at the Asian level, China's sport (in general, nit just football) was impoved, which means there are programs to improve football as well. However, Japan and Australia aren't weak teams that China can easily defeat, so that might be another reason why China failed to qualify.