Should people wait until credit-card data or PII is leaked due to security vulnerabilities? The problem with security is that it impacts more than just the programmers using the framework, it impacts everyone. Does the author deserve the nastiness? No. Do security issues need to be reported, and if not fixed, called out? Yes, for big and advertised projects issues like that need to be reported. If not, there will be users that would naively expect the web-framework they're using to be somewhat secure.
The framework had a professional looking website advertising the project, it had good documentation, a user-friendly API. It advertised a actix open-source community. Had over a million downloads. I would say that expecting actix to be run like a somewhat professional project is not a strange assumption.
The way it was called out was pretty terrible though, and I doubt anyone is happy with what happened.