What makes it appealing is you know every item in the game is obtainable. Every repeat boss run or MF run you do something good can drop.
The dopamine slot machine was done perfectly in D2R along with satisfying builds and great overall balance of classes. Every class has an OP build, items are never the same and have sometimes 5, 6, 7+ affixes that can turn a random find into one of the most rare finds ever found in gaming history.
People say they can get bored with Baal runs, but at least it’s designed that he, his minions and any elite within the Worldstone Chamber levels/Throne of Destruction can drop any TC87 unique item in the game. That’s a prospect that this game doesn’t provide. Target farming
Build diversity in D2R is simple and yet it completely allows for more diverse builds than a 58 point skill tree + 225 paragon points from D4. Why is that? Well David Brevik designed the skill tree with the idea of how tech trees worked in games like Civ and Age of Empires. Then even later down the road, they added the simple fact that “maxing out certain skills added a buff to a main ability you’d use.” Even with that simple, simple change, the level 6 ability became a staple use ability (ice blast for example on Blizzard sorceress build) because it’s damage scaled properly due to the other skills you maxed out to make Blizzard the strongest in the arsenal.