alt Hacker NewsAs far as alternatives, I wonder if anyone has tried a screen that cycles through colors in a known sequence. Using this modulating-color screen, it might actually be easier to separate the subject because you get around the "green shirt over green screen" problem. You might even be able to use a time sampling to correct the light cast on the subject from the screen as you would have a full spectrum of response.
I could also imagine using polarized light as the backdrop as well.
the general problem with any technique that isnt just throw some vaugely green thing behind our actors is that setting up complicated tech like this on an actual film set is extremely expensive. both the time it would take and the risk of it not working. so you end up with a dedicated permanent stage install but now you need to get the actors and crew to that place. better keys isnt a bad enough problem to justify that effort/cost. even the highly touted "virtual production" mandalorian stuff where you just put a big led wall behind the actors has shown to be more expensive than traditional vfx unless you tightly control the creative or approach.