Personally, I felt like he was a more "normally" designed souls boss fight in a game that feels FAR better fighting human enemies. Once you get parry mechanics down you can kinda cruise through most of sekiro, but with demon of hatred he involves WAY more dodging and jumping in a game where those just don't feel as good. Combine that with a huge healthbar, 3 phases essentially, and it was kind of exhausting to play compared to other bosses. It turned into a lot more trial and error like a normal souls boss, where you kinda just bash your head against them until you learn all the moves.
Did I hate it? No. But I have no desire to fight it again. It was fun as a 1 off fight, whereas I would happily fight most of the major bosses in sekiro again no problem. It's a fun change of pace (and I like how powerful some of your gadgets like the umbrella can be in that fight) but it's not something I'd want to do again.