I think I would rate it as a 3.5 of 5 right now. It looks great and combat plays really fluid, and your character looks great! There are a number of issues underpinning it that together make me not as invested as I was with Diablo 2 and Diablo 3. I'm not super hungry for spare time to play Diablo 4 but I think it's "fine".
However, I think Blizzard will have some nice updates to come because my problems with the game is echoed by so many others, like itemization, skill and build variety and high-level end game progression. In these regards, I wouldn't be surprised if we're looking at a vastly updated game already by autumn.
So that's why I'm happy that the core of Diablo 4 looks and feels good because that'd be harder to fix than the spreadsheet-like data.