I tend to try and see the bright side of Super since it got a bit of a bad rep, but Jiren straight-up bored me. His only gimmick is being too strong. He is shonen anime's biggest problem personified : if you keep making overpowered enemies, the protagonist will have to become overpowered too to defeat them, so the new enemies will have to be even more overpowered, and so on.

Comparably, Hit felt much more interesting despite not having much more of a personality as Jiren, because his timeskip made the fights interesting. Goku actually had to use his head to fight and not just have "become stronk" as his strategy.

Omega Shenron had a legitmately cool design and problably one of the few good ones from GT.
I remember one saying that Jiren looks like a background character or cannon fodder for the protagonists.
Everything about him felt so rushed.