Imagine if Kylo had straight up killed Palpatine at the start and been the primary antagonist. TLJ turned all the villains into jokes, with Hux being ragdolled around, Snoke dying like Jar Jar, and Kylo throwing a tantrum at Luke. Phasma not so much, but she was wasted too, so…
Getting Kylo back on track to be a genuine threat would’ve helped raise the emotional stakes and made his evolution over the trilogy more interesting.
Unfortunately…I don’t think this is editable with current material. Probably 10 years away to be able to edit that with deepfakes and video games.
That was the intention with The Last Jedi killing Snoke, to set Kylo up as Episode IX’s main antagonist. That’s what Colin Trevorrow’s Duel of Fates did as well. I think that was the prevailing idea forward until Abrams’ came back.
Of course, Treverrow’s script didn’t handle it particuarily well either, contriving an excuse for Kylo to get an even more Vader-ey mask and having him lose the final fight because Rey becomes a bad fanfiction grey Jedi using both the light and dark, and with later revisions pulling the ‘last minute turn to the light’ and making one of the Knights of Ren (coincedentally, one that was very much not visible during the flashback in TFA, because a) she’s a woman and b) she has the darksaber) be the eleventh hour final boss.