Fair use has nothing to do with this. Fair use has to do with distributing a copyrighted work. Emulators are (ideally) running completely original code that isn't copied from the company's source code. This is why, for example, PCSX2 has you use "your own" PS2 BIOS instead of including it.
The PS2 BIOS is copyrighted, so it's illegal to distribute it (and it's never been "fair use" to distribute it). But it's not illegal to do whatever you want with it (including dump it) as long as you own the console you're dumping it from and as long as you don't upload it to the internet for the purpose of distributing it to others. As far as the law is concerned, you bought the console and can do to it whatever you wish, provided you keep it to yourself and don't distribute it to others.
Games fall under the same category. You're free to dump your games and play them however you wish, provided you don't distribute the dumped game to other people. However, companies are also free to implement measures (DRM) to stop you from doing that as much as possible, likely because they know more people would illegally distribute them if they didn't.
I say this as a die-hard 3D Zelda fan:
I was soooo boooored in BOTW! There was no current main story. It all happened in the past. You're basically playing through the climax the entire time. And I hated it. I mainly play Zelda for the story, and this was a very poorly told one.
TOTK was somewhat better because it gave us better characters (I will die for Tulin), a bit better characterization (I enjoyed Zelda getting a lot more fleshed out this time), and a somewhat better story... but there were still way too many reused story beats. That is to say, the story was fleshed out much better, but they still reused the overall story structure from BOTW (get the memories fight the four bosses in the four temples, etc.). They did add a fifth temple and a mid-game story thing, but that's mostly it. They also didn't even acknowledge how similar some things were to their counterparts in BOTW (ex. the ~~Malice~~ Gloom), which really bothered me. Also, some stuff just felt... unfinished. Like the reporter bird who, by the end of it all, just ends up pondering and trying to figure himself out... and that's it. It felt like setup for DLC, but there wasn't any.
... That was a very unintentionally long rant.
To summarize: hated BOTW; somewhat enjoyed TOTK, though it could've been much better.