This question already has an answer here:
Although most examples here come from or are potentially from the Skywalker line (which may or may not make their offspring more powerful),I want to ask, why is it that the Jedi order (before the events of a New Hope when force-sensitives became a rarity and they trained literally anyone 'cos, you know... no choice) thinks it's better to train Jedi at a young age?
Yoda complained about training Luke at the age of 19 in TESB, and even declared an eight-year-old Anakin to be too old. However, both turned out to be extrememly powerful Jedi, and even an untrained Leia was proficient at sensing events through the force.
Although I hate to bring this up with no clear answers yet, but maybe it'll be pertinent in the future: Rey, who received the least amount of training, was instantly able to master Jedi mind-tricks (which stumped a similarly-aged Ezra on his first- and conscious- attempt at doing so), great lightsaber fighting skills and Force abilities.
Is it simply because these Jedi were of the Skywalker line that makes them more powerful -passing on those (whispers midichlorians) like a pro...?
Why not allow users to develop both mentally and physically before teaching them about the Force? After all, Anakin- the youngest of these examples and longest trained- was not a liability due to his age, but due to his mental instability.