Replying to myself with an update:
I spoke to the lead engine programmer and we're going to be making a series of changes that address the problems people are describing. These changes will all have trade-offs in terms of other factors like memory usage, but we'll find a sweet spot where the game looks perfect and performs well. The end goal is that slower computers will have longer load times and slower (stable!) frame rates, but everyone's experience looks good and plays smoothly. In terms of timeframes, I'm hoping it's measured in days, but we'll update you once we have a better idea of timing.