I don’t know, I think “Kylo Ren is the big bad of the third movie” was just as valid a road to go down as “Kylo Ren gets redeemed” - keep in mind that the concrete notion of “Star Wars is a story of redemption” was more or less retconned into the meta-myth about its creation by a typically unreliable narrator (George Lucas) and the Prequel Trilogy only really exists to canonize that interpretation and sorta/kinda justify Anakin’s actions - which is not a great choice.
Considering Abrams’ predilections for hewing closest to the OT in terms of tone and storytelling notions - the idea of the story being ABOUT redemption doesn’t really track with what the OT story WAS about. Vader was redeemed (ish) in that trilogy, but the series wasn’t ABOUT his redemption. It was about Luke fulfilling his journey to become a Jedi and save the galaxy from tyrannical evil. Vader turning back to the light was more like his own reward for fulfilling that goal, not the overriding thrust of the story up to that point.
So insisting that Kylo Ren HAS to be redeemed because “that’s Star Wars” rings false, to me. Vader didn’t HAVE to be redeemed until somewhere about the halfway point of the last movie in the OT. And really, that option didn’t even exist until Lucas decided that the best possible cliffhanger to keep his trilogy viable would be to spring “I am your father” on the story out of nowhere, with no setup or prior lead-up to that moment in either movie to that point. Vader’s redemption was never the point, but that it still works is a testament to how good at their jobs everyone was at the time they were figuring out how to un-knot all these story elements for a happy ending.
But with Kylo - I feel like there are absolutely ways to tell a Star Wars story where the bad guy doesn’t get redeemed, where his tragic, misguided actions serve as an object lesson on what not to do and how not to be all by themselves, without the absolution of forgiveness and redemption layered over the top of them.
Granted, they didn’t take that route, and that’s fine. I wish they’d executed the redemption WAY better than they did - but I don’t agree that an ending where he’s the bad guy, and dies the bad guy, is fundamentally anti-Star Wars, or invalid on its face, either.