There’s no way I’m logging into rando apps using my GitHub id. Aside from their bad UX and the potential to accidentally over grant permissions, the app could abuse GitHub ToS with my credentials and get me banned.
Not worth the risk just to play around with a site.
The sign-up form doesn't seem to allow passwords with non-alphanumeric characters in them. Ironically, when it sees one, it complains that "password must have at least one number and at least one letter" (even though it already does) - I suspect that's just a catch-all message for invalid passwords?
In any case, the restriction makes it incompatible with pretty much all password generators, including the built-in ones in modern browsers. To improve matters, I would suggest dropping all restrictions on what cannot be included altogether.
Logging with GitHub is still lowish but like 1k per hour or so. (IIRC)