It was pretty shallow and generic in my opinion. It was rushed through in about 2-3 minutes when it could have easily been expanded on.
It could be salvaged if it was revealed that Belmod was the one who killed Jiren's friends (as some have suggested) or if Belmod and Jiren created some way to get jiren stronger that was messed up in some way. I don't want Jiren to be another character ruled by revenge