You don't need any of that. From how the game scales, the most important thing is the gears unless you're a mage then it becomes "Chain Lighting" and "Meteor Shower unlocked".

The scaling from level 9 to 15 on gears is already huge, you get like 20-25% more damage per level if you always upgrade your gears. On level 17-20, this jumps even higher and so does your magic damage especially with skills like Meteor Shower that does multiple hit, or stuffs like Chain Lighting or Epidemic of Fire that will chain over and over until there's only one target left or it runs out of hit.

Even a subpar build will deal good damage if they have the highest level weapon available. It's one way to keep the player from just going from one area to another without exploring at all. The amount of legendaries/divine/unique left all over the map is almsot good enough to keep people geared without buying and if they use thievery/magic charm, they just get those even faster (too fast tbh. I'm trying out magic charm and that thing proc every 15 minutes or something)