So the gist of the post is, if you want to "count" for Firefox developers, you better share your usage data with them? That attitude is... not great. The point of making telemetry optional is to respect the users choice, not to say "well you can turn it off but then we do not care about you as a user any more and we'll make your life harder by killing features you rely on". This is exactly the kind of attitude we are seeing way to often when it comes to giving consent to gathering and processing user data; I expect Firefox and Mozilla to be better than that.
To me, this is a cautionary tale not for Firefox users but for Firefox developers, who have to learn to deal with the fact that telemetry only reflects a (non-uniformly chosen) subset of their users. If you removed a widely-used feature due to unreliable data, the blame is on you for relying on the data too much, not on users that used their agency to make a choice.