Kylo is the only good character in the sequels, his arc is the only unique character arc in the sequels. Rey was an Anakin ripoff, Poe is a less funny Han Solo and Finn is just wasted potential. Snoke and Zombie Sidious are cheap imitations of the emperor we all know and love. I also hate how they couldn’t give us Luke, Han and Leia on screen one last time.
There are several reasons for this. The first is that Han left him to train Luke, and he went off on his smuggling adventures. The second is a traditional Sith ritual. Kill what kept you on the light side and completely plunge into darkness. In the end, it only broke Ben.