The age question is one of abundance and luxury, the prequel era Jedi have their pick of the litter so to speak. They can afford to make hard choices about who and how they train their next generation.

They're strict because they're not applying the rules to a group of thousands of people they're applying them to a literally galaxy of force sensitives and they have finite resources. If you have 10,000 knights then you may need 7 or 8,000 starfighters, quarters, food, cafeterias, energy and so on. The Star Wars Universe is not a post scarcity society.

Equally the great contrarian of your order shows up with a boy and claims he is the chosen one. This is a man that argues every order he's given, doesn't respect the chain of command and has been wrong in the past. Do we really expect the high council to just accept this without question.

Honestly I think this sub is too hard on the prequel era Jedi and give too little though to the realpolitik running 10,000 strong (rebels) organisation that's existed since at least 25,000 BBY. Our own politicians appear to be out of touch after 8 years - Yoda had been a master for 800 years and