Turning the feature on by default is bad, but I don't think that legal complaints are the way to go as well as the aggressive tone of NOYB. Firefox is the only browser developed and maintained professionally which has the potential of offering some privacy on the web. Given the importance of web browsers volunteer work just won't cut it with the amount of features and security concerns that a browser needs.
NOYB would've done much better by talking to Mozilla directly and advocating for them to do the right thing going for a legal complaint as the final nuclear option. If the was the case, then good that there's a complaint, but the article does not indicate the any of this happened.
Right, but what other browser are you going to use?