The sunken cost fallacy at work. You are now putting time into a game you find unrewarding in addition to the money you put into it. That’s not good.
If you value your time, play other, better games. You’re wasting too much on D4.
p.s. FWIW, D4 could have survived a lot of the problems it launched with if it had a good loot system that players found rewarding. But as we know, it doesn’t. It’s perhaps the worst aspect of the game when it needs to be the best. That’s true for all games.