Golden era was around 2005-2010 when Mozilla was running product innovation experiments such as Ubiquity or Tab Candy, "Design competitions", sending "Thank you" cards to beta testers, people like Aza Raskin having regular blog posts about development... My oh my, looking at those in archive.org and seeing treasure throve of comments, 100+ on each post, the excitement in the air with each new announcement feels just magical.
Roll forward 15 years and Mozilla Labs is about AR/VR(?), interaction with Firefox is through 3rd party sites like HN and real product innovation stagnates for years.
The real reason Firefox is losing market share is a simple fact that it is inferior to its competitors as a product, which is the direct result of this loss of connection with its userbase that it had and the passion for creating the world's best, most innovative, browser.