I agree with this opinion piece. Firefox is a product strangely hostile to its core userbase. It's almost like they've been deliberately trying to sabotage themselves for years. I don't use it because I approve of all their stupid pigheaded UI choices, I use it because it has been the least bad option despite those choices. That might not go on for much longer, though.
Judging by the HN and Reddit comments with each Firefox/Signal/Matrix releases, it seems most of the customers of privacy focused products want all the other features of competitors; most of the times without paying any money (or they think donations should cover for everything because they once donated, so all hundreds of thousand users would). And they dislike/have negative sentiments towards any UI changes or breaking functionality for new features. So core userbase for these products becomes hostile towards the product growth by definition. In this environment, either the product stops growing and simply becomes a niche product for those set of users or it dies.