And regardless, it’s a fucking movie in space. Quicksand doesn’t have to follow Earth rules, because the movie does not take place on Earth. So no, quicksand in a desert is not impossible because it’s not an Earth desert.
Certainly anything is possible. If Abrams would have cooked up a thing where Chewbacca turned out to be Ren’s true father because the midichlorians modified Chewbacca’s wookie sperm to be compatible with a human egg, you’d be arguing that that would be fine, too…because after all, in your own words, “It’s a fucking movie in space,” and sperm on Jakku or Takodana do not necessarily behave as sperm do on earth.
Let me know when you can link to a video explaining how quicksand works on Jakku.
This is where we get into the ugly realm of what is possible vs. what is plausible. Unfortunately, it seems that some folks here aren’t able or aren’t willing to discern the difference.