This is honestly quite mild by website bloat standards. If that’s really the entirety of their Javascript it’s already way smaller than e.g. Medium or what this blog post considers “slightly bloated”. The fact that it’s in one file in 13 lines is also very standard. It makes no difference to the parser whether there are newlines or not, and removing them will in fact be saving bytes.
I’m guessing the performance issues with the site are more to do with how it’s coded. If it’s really bad for what sounds like a simple use case it might even be a cryptominer or something. A lot of those “random utility as a service” sites are.
That’s just a one-time pad with extra steps.