Whats bad and what needs to be fixed? Rather know it from you then some youtuber
Microtransactions are not the problem, let me tell you that up front. They might be part of the cause of the problems but they arent why the game is dicks.
So the biggest issue is that stats are broken. Elemental resistance doesnt work properly and the enemies deal way too much elemental damage. Blizzard said it will take months to fix this. Also their damage calculation for player stats is broken, making one or two stats in the game far and away the best stats for gear. Blizzards solution to this was to nerf the amount of these stats that gear could have by 65%, effectively they nerfed player power by 65% across the board and didnt fix anything else.
What this means is the players are weak and squishy because they nerf our offense, and our defense is broken so we just die.
Additionally stash space is extremely small because they thought it would be a good idea for the game to load the entire inventory and stash of every player on screen at all times. Meaning if they gave us a lot of stash space the game would crash if too many players got on screen.
There are no activites at endgame outside of spaming dungeon keys over and over again. Because they nerfed the exp from every single other thing in the game. Making endgame super reptitive.
The legendary effects are broken and the best items in the game are so rare that only 3 people in the world have gotten them to this day. There are 9 uber rare items and literally only 2 of them have dropped ever meaning nobody in the world has seen 7 of the uber rare items ever. You have 1 in 5million chance of getting these items once you are over level 85. This for a game that resets every 120 days.
There are other design choices that are unbelievably stupid coming out of a studio with this much money and experience that there are no excuses for it.
Go play Path of Exile instead.