Otherwise if it's just on a whim of the lead dev, that often does not scale. And we've seen with lots of projects, that actual regular-user feedback, not power-users, is crucial in taking those decisions. Switching off telemetry is easy, but I suppose you also have concerns about technical issues, and those can be really difficult to compromise on (a lot of people suggested forks when XUL was removed.. but today probably very few people would want XUL back).
To have a successful fork, you need devs with either a business model behind it, or enough motivation to maintain it as a hobby. For a while, it worked for Iceweasel, but it was just branding. Firefox is complex, requires a lot resources to build, distribute binaries, etc.
I'm not affiliated to Mozilla, but I do help maintain another open source project, where, in my opinion, power-users and consultants drove the project in a direction that made the product more difficult to use, and therefore gave it a bad reputation and limited growth. I can say that because I have access to some of the telemetry, and also because I talk to a lot of random users as part of my work.