No surprise, as a diablo fanatic(close to 10k hours spend between all games in the series, i even tried diablo immortal for an hour or two;p) who preordered game in december, and played 20h of beta on top of 150h+ after launch, game has 0 lasting power after u beat intersting story/finish sidequests/explore map.
IF grinding and itemisation is no fun any hack&slash game will be no fun either, till they fix it in some major overhaul(maybe with expack?) but for that u would literally need to fire some head dev responsible for making decisions and hire/let new one who actually likes diablo games for what they are- fun and exciting grindfest.
I repeat- its not some programmers who fucked up with decision, its person(maybe group of ppl?) who gave an OK to overall itemisation and griding systems in the game, those feel like extremly nasty chore and provide u with 0 dopamine rush, they had amazing template how to do it in d1, d2lod, poe and d2r, yet they made it even worse than in d3, much worse.