It's fun by my standards, but the grind is pretty intense

That's true.

It only starts getting fun after you finish all the treasure hunting.

That's true.

Still, once you get past a certain level, it gets fun lol

After all the grinding, Gurre, Shinre, and Makai are fun, but the problem is there's not enough content once you've done everything up to the current Legend. The labyrinth and dojo are problematic because of the cheaters.