Depends what its to do tbh. But nothing cuts and clears mud much better than a Mud X. They’re shite at everything else mind but for what you describe I’m not sure anything else will be much better. Slow riding in sticky mud is a recipe for clogging basically… The reason other tyres like the shorty etc are more popular now is that they’re almost as good at crappy mud, and better at everything else, (personally if a Mud X is the right tyre for the ride, that ride can **** off, I’ll go somewhere the Mud X isn’t the right tyre and have fun instead)
But, something like a shorty might work, just because you get a bit more paddle, and the rubber itself’s grippier so they can make more use of even small bits of grip. I’ve a feeling you’re basically using the right tool for the job already though and it just happens to be crap riding conditions.