Instead of a player deciding how they want to play their character

This ended up with the Diablo 3 that players are Diablo IV Gold familiar with today, with minor additions or tweaks to Diablo 3's systems coming in periodically such as the Follower rework and the addition of Ethereal items. 

Though many fans would agree that Diablo 3 is in a better state now than it was before, for many fans Diablo 3 doesn't have the same satisfying staying power that Diablo 2 has, and fans are hoping Diablo 4 will fix this.

One major problem for Diablo 3 is the lack of interesting items for players to find. If a player wants to use a build that is viable in any end-game content, they will need to more likely equip a Set of gear. The rarities in Diablo 3 go from Common, Magic, Rare, Legendary, Set, and most recently Ethereal. 

Very quickly a character will begin equipping Rare and Legendary items but it is the Set items that will allow a player's abilities to go beyond what is normally possible. 

Instead of a player deciding how they want to play their character, and then finding gear to facilitate that, they are instead forced to play a certain way due to the limited viability of the available gear. This is a problem that Diablo 2 didn't have and Diablo 4 looks to Diablo 4 buy Gold solve by introducing compromises for each rarity of items so that players don't simply flock to the highest tier of equipment.