That math doesn’t math. He was directly responsible for 2/3s of it, and the other third he plowed over.

Read this again:

You claim I say Rian fucked up the Trilogie, he didn’t. He only fucked up 1/3 of it.

I'm saying Rian only fucked up 1/3, not JJ.

Rian’s explanation was fine.

I sorta disagree. Other possible explanations aside (I dunno, maybe Luke went to undertake a serious ritual and didn't want to get interrupted unless absolutely necessary) this explanation demands a lot more elaboration. The concept is fine but it would need some more fleshing out (I would prefer a short movie) to pick up the audience. The gaps between Episode 6 Luke, Flashback Luke and Episode 8 Luke are too large to bridge with suspension of disbelief/imagination for some. The trajectory many thought Luke would take does not match what we are shown, which means the audience should be shown a bit more to adjust that trajectory. The audience needs to see Luke drift off first before this transgression, not just told it happened. We do not need to see Luke attack Kylo. We need to see him drift off into intolerance to narrow the gap between Episode 6 and the Flashback. As it stands we see Luke on a trajectory to heroism in Episode 6, then an angry old man in the Flashback and someone who recognized the error of their ways in Episode 8, the difference between Flashback Luke and Episode 8 Luke is fine but the difference between Episode 6 Luke and Flashback Luke is not. His character makes a complete U-Turn in between and we, as the audience, have not a single clue why. It does not match the character we know to such an extreme extent that is completely takes you out of the movie. There was just not enough time in that movie to fit such an Arc for someone who is a Side Character+.