I don't get the "They ruined Jiren!!!" complaints; if anything him snapping like he did reflexively makes him a (slightly) more interesting character to me. Dude had almost zero personality and then they decided to double down on the blandness by giving him the most generic, boring tragic backstory you could possibly think of.
I think the decision to make him so pathologically obsessed in the idea of "Justice through strength by individual merit alone" that he snaps after seeing Goku surpass him with the motivation of his friends and family gave him a much needed infusion of some kind of personality/character that he'd been missing up to this point. I like how it exposes him as hypocritical in the light too; he talked shyt and condescended to Toppo for losing to Vegeta while abandoning his Pride Trooper ideals and going full on god of destruction. But when he was in the same desperate position Jiren did the same thing but even worse by trying to fade every innocent U7 bystander just cause Goku had him mad giving him that work with their support. Got his ass beaten in more embarrassing fashion too
I think what Jiren revealed himself to be is a lot more interesting than just the generic "stoic, quiet unstoppable warrior" jank he was for all of the arc up to this point.