3> “Filling in the canon” or “The George Lucas Error” —Strangely enough, this is a problem that the current movie series has somewhat avoided, by explicitly calling it a different time line. One of the problems with Enterprise was its impulse to hew to canon and “fill in” events that we knew happened or must have happened. This is one big reason why the Star Wars prequels were so tedious. Story should serve story, not canon.
I don’t think that is a problem at all. Enterprise was notoriously poorly-received in its earlier seasons because it kept avoiding known Trek canon. The Temporal Cold War and the Xindi stuff particularly annoyed critics. Once they started dealing with familiar Trek territory - Vulcan, the Andorians, mirror universe, a Gorn showing up, etc. - fans were much more receptive. Of course, by that point, the show had fallen out of favor that the rally was unable to save it.
Likewise, Star Wars: Rebels has been pretty good Star Wars material. And the two different Clone Wars series were fairly good in their own ways. And all of those are “prequel” series. Rogue One coming up is also a prequel, and looks promising.
The problem in common for both Enterprise and the Star Wars prequel trilogy is bad writing. People are more than happy to indulge in canon-spelunking expeditions if they’re enjoyable. No one is interested if said indulgence comes with mopey Anakin, Jar-Jar Binks, or snoozariffic Hoshi and Travis.