Closed Unplayable Performance

I picked up Starbound ages and ages ago when it was still in development. I played it a couple times while it was in early development and saw a lot of potential, so I set it aside and waited for it to mature a bit more. Fast forward to today when I have some free time, and, much to my dismay, I fire it up to discover that it's completely unplayable.

The menu runs great, but as soon as I load any game it goes all wonky. The tutorial level never runs any faster than about 10-15FPS (imagine playing at half speed). A new character that skips the intro mission runs at about 10-30fps and swings between the two extremes every second or so.

Just to be on the safe side I uninstalled my copy and installed a fresh version of 1.2.2 to no avail. It's not like I'm running under-powered equipment either - I have an AMD FX-8120, 8GB of RAM, and a GTX 970. I've done some pretty exhaustive research on this, and it appears that some people had this kind of performance last year, but there wasn't any mention of a patch or fix for it other than to use the OpenGL launcher (which I can't find, since there is no longer a splash screen menu).

Is this a known issue? Are there any fixes for it? It seems like a great many people have no problems playing Starbound, so I have to imagine that this is an exceptional case. Does someone have better Google-fu than I do, and knows what to do?