The shift to an item-based focus is what I didn't like about D3. Obviously gear can make or break builds in D2, but in D3 almost the entirety of character progression was based around gear.

Sure you unlock skills as you level in D3, but once you got to the appropriate level changing your build was as easy as clicking a couple buttons. All the skills were gear-based, and sure certain items worked better for certain skills but once your character was leveled there was little reason to level that class again because you could easily swap skills around and just have gear swaps in your stash.

D2 forced you to think about the character you wanted to play and actually build into that character. Once you did it wasn't easy to change your character, so it encouraged replayability by forcing you to remake the same class if you wanted a different build. The only way I spent years playing D2 was due to this, such as leveling up a paladin into a hammerdin, leveling a different one for boss killing (smiter), and even a third as a zealer. In D3 this would've all been accomplished with a single playthrough and some gear/skill swaps depending on what I wanted to play. D2 gave a sense that a character has a specific purpose to me, D3 was just "idk do whatever you want whenever you want" so the characters felt boring and had no real meaning behind them.

That said I still did enjoy D3, I just felt like it was well behind D2 in terms of replayability. I played D2 for 4-5 years when it first came out, I played D3 off and on for maybe a year, and a good chunk of that was to make a little bit of money when the real money auction house existed.