There is still problem with switchable GPUs: namely those, where one GPU is using Mesa and the other is not (i.e. Nvidia). Those computers didn't disappear for the face of the Earth, people are still using it and expect it to work, even if there are never laptops available on the market. It is being worked on (https://blogs.gnome.org/uraeus/2016/11/01/discrete-graphics-...).

Do you have a source for this? In any case, just because some hardware has been recently phased out doesn't mean the manufacturer shouldn't be expected to support it. Not everyone has enough money to buy a new computer every year; I'm a student with an Optimus laptop and I know I won't be able to afford a replacement in the next year or two.

If NVIDIA can't be asked to fully support their hardware on Linux, the least they can do is release some documentation so the Nouveau devs don't need to grope in the dark.