That’s how it starts. Mozilla itself is maybe not hindered on its mission, but the people who depend on them are: the extension was blocked, and there is no official way that I know of to add third-party extension repositories to Mozilla. And sure, the more important part of the problem is you cede just one bit, but the authoritarians won’t stop. They know now Mozilla will spread their legs so they’ll ask more and more, and Mozilla will for sure choose to bend over for them than to act for the people they were supposed to be fighting for.