Hot take: It's not just Diablo 4 that has boring moments. Too many modern Isometric ARPG games are way too long, bloated, and/or grindy and it gets quite annoying. This includes everyone's favorite, Path of Exile.
I think most Isometric ARPG devs have figured things out gameplay-wise, and the genre itself needs a big shakeup from a storytelling standpoint. The genre needs projects to entice people who normally don't play ARPGs to give them a chance, other than just being the popular 'flavor of the week' game.
Another genre, JRPGs, I barely play anymore(or play very, very selectively) has reached that same stagnation over the years, but all it takes is a bit of creative spirit to make me pay attention. Look at how Eiyuden Chronicle is making a smaller budget JRPG experience feel dynamic, cinematic, and engaging when it comes to scenarios:
I don't even know what this game is about, but it's making me actually pay attention to a genre and type of game that I'm normally not interested in. And that's the point. I just need ARPGs to spice things up a bit more instead of giving me a couple of high budget CG cutscenes and then asking me to go hit some low level rats and skeletons again.
I didn't pick up Diablo 4 nor did I even come close to thinking about it, because there was nothing I saw that was enticing from the outsider perspective. I thought fans of the I.P. would enjoy it and eventually recommend it, but they quickly turned on it after launch. As an outsider, that makes me want to not even bother at all. Something has to change.