Privacy always comes at a cost. We are all different and have varying preferences based on our experiences and perspectives. Deciding how much privacy one wants to give up for convenience or other benefits is a personal choice. There’s no need to judge others for that decision. To each their own.
I appreciate your detailed description of the probable benefits of telemetry. While I acknowledge there are benefits, however, before accepting a given set of telemetry, I would like to know with sources and in exact terms (not just ‘improved UI’) what enhancements were made to Firefox that couldn’t be achieved without telemetry. I want to decide for myself if those features are truly important enough to justify sending my personal data to the developers. Only then can I make an informed decision, and it still wouldn’t necessarily mean agreement. It’s not paranoia; it’s simply refusing telemetry for any reason given.