The emulators have always been in a gray area, since they can play illegal copies of games with illegally sourced bios, etc. The emulator itself is simply the tool, which on its own isn't proof of piracy much like owning a bong isn't definite proof you smoke weed... just very suggestive (it can be used for tobacco I guess?)

As for current vs retro gen piracy, they're equally illegal but obviously criminalized differently. And the ethics are obviously complex, you have people who pirate who otherwise wouldn't be able to pay, you have people who pirate for a convenient copy of something they already own, and maybe people who could pay but simply don't want to (although research has suggested this isn't a huge group). And since it's digital, there isn't a loss in the same way as actual theft.

Personally, I just like taking control of the hardware and tweaking shit. I belong mostly to the folks who download copies of things I've already "bought" (which is a licence in many cases, as they don't sell physical copies). A good example is Pokemon Scarlet, which ran like dogshit on the original hardware. I've been meaning to try it in an emulator to see if it works better, although I haven't bothered yet. Would that be considered immoral, given I own the game and several switches?