I just wonder if the whole concept of ‘cute 9 year-old transitioning into evil warlord’ was too much for Star Wars to handle whilst keeping things family friendly. It’s one thing to have it all implied in the OT, but it’s another thing to actually attempt to depict it.
For example my other favourite movie, Conan the Barbarian, does it perfectly. Conan, as a 9 year-old, sees his parents and kin slaughtered by an evil cult, is thrown into slavery (real slavery, not the suburban TPM version!), then sold into gladiatorial combat before being freed as an adult. Throughout this experience he is entirely driven by vengeance. There’s your Anakin. There’s a guy who legitimately could become Darth Vader. If Obi Wan had met that guy on Tatooine and they’d established a friendship, and then Anakin had been forced to choose between revenge and Jedi pacifism (maybe the guy who had slaughtered his parents had seen the light and become a Jedi Master for example), right there you’d have the perfect catalyst for a clash of ideals between legitimate friends/allies. But it would be dark stuff…
Making a movie aimed at children with dark elements is something nobody seems willing to do these days. The Neverending Story and The Dark Crystal are examples that come to mind. Those movies wouldn’t get made today.