The Emperor is the head of the Empire, which was the main threat of the original trilogy. Another separate threat would be introducing a new and separate antagonist. Lucas never did this. Snoke and the First Order was the primary antagonist, setting up Kylo to supplant him. Having an extra force to fight against that The First Order also has to fight against would have convoluted everything, be that threat another force or Knights of Ren.

TFA establishes Luke was ashamed due to Kylo turning to the dark side and that’s why he went into exile. It’s in the crawl and repeated in dialogue from Han.

No one lost the ability to use the Force, if anything it’s more widely believed in during TFA than ANH. Even non-Jedi/non-Sith characters use the Force (Maz).

Kylo is the leader of the knights of Ren. That is the only thing we know about them outside of the Kylo Ren comics.

I’m just saying that Johnson developed what Abrams introduced. If you have a problem with what was introduced, your issue is with Abrams not Johnson.