I think the fact they use submarine-swaps is biting them in the ass. Unfortunate but it is what it is. I think, at the time, submarine swaps made Muun stand apart and solved some interesting limitations while the Lightning network still grew.

But as the timechain fees (and usage) increases, and with lightning much more robust than it was 1-2 years ago, maybe Muun's way of handling things aren't the best way anymore.