Mokas are a finicky beast. I’ve had it make some of the worst and some of the tastiest cups I’ve had. Is it acidic or bitter? It’s easy to burn it, but that doesn’t sound like the problem. I’m guessing it’s too fine. Every bag I got had to be individually dialed on, but in general I found a grind much more similar to drip/ pour over worked best. I’d try that. Fill your filter up to where there’s a good mound and lightly tap down with a spoon.
Also, have your changed your filter and gasket that go into the top portion? Those can get old grinds stuck in it easy that can taste off.