Also pretty sure the art style choice is partially to compensate for the dev's lack of resources and optimization expertise, so I wouldn't hold my breath for optimization.

Believe it or not you DO NOT NEED a moat to defend your base. You can defend your base purely through try-harding the combat. Moats create a HUGE amount of lag so if you're losing a lot of frames that could be the reason. Like, even digging a dock out or adding an entire extra land-mass out over the water doesn't cause as much lag as a moat does.