This goes into way more technical details: https://ascmag.com/articles/the-Mandalorian Particularly interesting is how the system had ~10 frames of latency, so excessively fast camera turns would show lower quality renders.
Umm, Ray tracing would love to have a word :P
In all seriousness, typical animated frames for big budget films easily take hours or longer _per frame_. It really depends on what looks you're trying to achieve. Game engines have come a long way in terms of realistic graphics with realtime rendering, but it's worth noting that it's still not the same quality as a fully ray traced scene (whether that matters depends on the content I guess)
After it is filmed, they can still go back and touchup the backgrounds. Someday with ray tracing they can do real time finished products, but for now the tech works great at what its intended to do.
btw. Only about 50% of the scenes were made with this setup. rest was traditional ray-tracing.
I wonder how many GPU's that system had.