Web-browsers are a lot better at auto-filling registration forms correctly thesedays, and now that even Office 365 supports disposable e-mail addresses means that registering for online services is far less of a chore than it was before. Also, many sites support federated identity (OIDC, Sign-in-with-Google, etc) which also takes a lot of the pain away.
I remember in years gone-by, before data/privacy-laws were either introduced or widely understood by web-devs that sites would have all manner of required fields just because someone from marketing or management thinks they need to collect everyones' home address, age, home, work, and mobile phone numbers, and sex/gender - now that they legally can't (without a good reason) things are a lot smoother.
So in summary, BugMeNot is gone because the severity of the problem it aimed to solve (online registration tedium) has been reduced below the threshold of action.