How do you know supersampling makes no diff?
Because I've tried supersampling before, and use it sometimes. I'm a complete autist when it comes to frame-rates and to texture shimmer/crawl. I've tried out any random thing you can probably think of to get rid of texture shimmer and crawl. It's something that's been bothering me since the early 2000s when I first noticed shimmer and crawl in some maps/objects in Counter-Strike: Source; I didn't understand why the game's MSAA didn't fix the texture crawl, and it always bothered me.
Also texture shimmer and texture crawl are temporal artifacts, they require a temporal solution. Maybe they'll eventually implement a temporal supersampling (TAA kinda is that already, but in a crude way), but until then "regular supersampling" does little-to-nothing for temporal artifacts like shimmering or texture crawl.
EDIT: By the way, temporal = between frames in gaming context. This is why things don't shimmer or crawl when you're standing still (unless the camera is swaying or the objects themselves are moving).
Also fast moving objects will be hurt by TAA
Yes, due to the temporal nature of the solution. More than acceptable comprise, and TAA gets better and better all the time anyway. Picture quality is the most important thing and you can't have good quality if you have texture shimmering and texture crawl.