>which is the reason why the browser is no longer so customisable.

That was the big one that cost a lot of users, but it was a jusitifiable big leap for them to take.

But they have also been suffering papercut after papercut power user losses with various regressions and removal of functionality since then.

The actual users lost are minimal, but I suspect the overall perception of Mozilla's priorities, among those kinds of users, has suffered much more.