I've seen it. I've made my opinion clear on the movie before. and it's "twist". (Which I'll reiterate, for fun)
So, It'd be more accurate to call Split a franchise movie apart of the "universe"
Split is a good movie that doesn't benefit at all from the movie it's tied to (for multiple reasons). Personally, I don't feel comfortable calling it original because of it's ties to other movies. That's just how I feel.
Perhaps the most entertaining thing, and it's a schadenfreude thing, is watching the predictions for JL go from 150+, and slowly slide down, and down, where it looked like maybe it'd hit 120 this weekend...
I suppose it could have been worse.
There was more than Armond knocking TS3 though. He was just the first.
(I do believe Get Out did get a second rotten at some point, but I can't recall.)