Mad to me that this hasn't been resolved after _years_, despite it seeming (naïvely) to be quite a simple fix?

I worked around it once—I can't remember how now—and got Inkscape running without lag on my Mac, but it introduced another bug where it would crash when resizing a window. I got done what I needed to do then abandoned it. I doubt chasing down the fixes would take that long for someone with actual experience.