I've got a Switch, I buy all the games that I play, and I am extremely excited for this emulator to come out.
In my Steam library I have several games that are DOSBox wrappers around the original title. They're emulators, and I paid money for them, and they're perfectly legal.
Digital archival is a growing problem, so much of our culture is going to be lost without efforts like these.
On a side note:
When I talk to fellow gamers about my history of modding games, there's generally two groups. The ones who play on PC ask what I added, new levels, skins, etc.... And the ones who play only on consoles typically get upset because they think it means I made cheats for online play.
(For the record it was usually new features in code)
DRM and proprietary drivers/blobs/formats are enemy to humanity. This is also why it should be (and in some places is) 100% legal to circumvent such measures, including via reverse engineering.
But it shouldn't be that way! I'd say society should go a step further and grant copyright on works only if the specification of the underlying formats is fully released, just like patents exist(ed?) to grant legal protection in exchange for disclosure.
[1] https://twitter.com/yuzuemu/status/952461671368478721