Just gonna add my 2 cents.
Emulation itself is legal.
Piracy (i.e. using emulation to play games you don't own) is theft.
Using tools to circumvent the protection on a piece of hardware or software you legally purchased is probably against the EULA, whether it's Nintendo or Sony. How legal those EULAs are is debatable and depends on your region.
For the record, I do use emulators, I have played exactly three games on Switch emulators (Ryujinx at first, now Sudachi): the Castlevania Dominus Collection (come on, games are antiques), Kirby and the Forgotten Land (wanted to see how well it ran, loved it so much that I went and bought it the next day), and Xenoblade 2 (modded, because fuck that bullshit treehouse localization/censorshpip), which I also own since release.