I've got a few concerns about the game maybe you can help me out?

I've seen a few reviews and watched some game play and the game play looks like I would enjoy it. I dont have any problems there but something someone said in a review made me think the game might be like Diablo. In the sense that your main driving force will be just to get more loot/skill upgrades. It seems like all you would do in this game is farm dungeons for 3% upgrades like you would farm rifts in Diablo. There is nothing wrong with that, I did enjoy Diablo 3, but I want more than that if I'm paying $40.

Like is there more incentive/progression than just incremental upgrades? Is there an endgame that you would use your incremental upgrades on or is it just for personal satisfaction? Is there a boss/dungeon/raid progression with the multiplayer?

Another concern is I saw this one guy mention that the game isnt very challenging once you start getting upgrades. Which makes sense, but I wonder how far in this guy was. Even so are there hard/challenge modes?

I guess TL;DR is: what is the carrot on the stick for this game? Is it just incremental upgrades or is there more than just that?

Let me put it this way I don't mind the main driving force being just more loot so long as it's not just mindless grinding. If it were like an mmo where you get loot from one dungeon to be able to do next dungeon, rather than just grinding rifts so next time you can do the same rift faster.

My god I am still typing! I hope that wasn't too much heck I hope anyone sees it! I want to play this game, but dont feel like regretting spending $40. Which I guess isn't much, but it's more about the principal.