The issue isn’t what D4 does wrong (in your opinion), it’s that you think every ARPG within this genre should be the same and follow the same rules. You have a very set and clear definition of what these games should be, what they should do, and if it goes against that you speak out against it.
Now your opinion isn’t wrong, but just as there are variations of any genre out there, D4 and D3 are just variations of this genre. Yes Diablo 4 and 3 both have ‘mandatory grinds’ if you want to increase the power of your character.
Just as other games have mandatory grinds of various activities to gain more power. D4 is singular in this case, where as other games offer multiple activities to obtain the same goal. That is what you don’t like. Which is completely fine. I just don’t see that changing anytime soon.
The game has been streamlined pretty much since S2 and beyond. As that is how the nature of Diablo games have evolved. When they deviate from this, as is seen with chaos Armor not being target farmable, people speak out against it.
This game and D3 have conditioned this audience to believe everything should be obtainable within reason. PoE and LE say otherwise. D2 in comparison was much simpler and required very little grinding to complete all of the content. There was nothing to push for in that game other than just random fun from loot dropping.