I got Diablo, my first run at the series, because one of my Overwatch friends was really excited about it. At level 32 right now and here are my thoughts thus far:
Likes:
Story - Coming into the world for the first time it's been fun following the characters and the story.
Look - Enjoy the look of the game, especially in the cutscenes and animations.
Character building - With plenty of skill points available I loved really digging into the skill tree and building out the character abilities and specializations that I wanted.
Dislike
Grind - From battle to equipment it feels like less a skill game and more a grind game. Combat you spam your stuff at the appropriate time without trying to get hit too hard. For equipment, I go out, complete a few things, fill up my inventory, come back, put on the best stuff, scrap the rest for parts, and upgrade what I have equipped. Rinse and repeat.
Quantity over quality - Hand in hand with the last point. From endless enemies and dungeons to equipment and weapons, the game just throws everything at you in droves. While I jumped ship from Destiny after the first game, I did love how in that the weapons and upgrades seemed to focus on hard fought incremental upgrades and different styles of play and bonuses carefully crafted from what you were equipping.
So overall, enjoying the time with my buddy and can overlook flaws to move through the campaign and enjoy the new world and story. But definitely would not make this a Destiny type game where I'm replaying as all the different roles and configurations and trying to replay and get every little accomplishment.