I don't intend to contest the capabilities or robustness of current generation of KDE, but it is not "strange" that KDE is not the default or equally popular if

I don't intend to contest the capabilities or robustness of current generation of KDE, but it is not "strange" that KDE is not the default or equally popular if you take its history into account. A lot of people have faced quite a few frustrations with both bugs and performance regressions when updating to new KDE releases in past. And it doesn't help that really awesome apps like Konqueror got discontinued. And also given the history of myriad shenanigans around Qt's licensing, it is not surprising that the open source community gravitated towards a platform (Gnome) that was built and evolved in the open. It is interesting that you compare this with Firefox, because these parallels can be extended to FF too. A lot of us moved away from FF because chrome was a breath of fresh air in terms of performance when it arrived and has since had trailblazing support for modern web standards. Sure both FF & KDE may be in much much better state now, but it is worth acknowledging that for the wider population there is a lot of inertia when it comes to foundational technologies that are critical for their day-to-day work. If it works, and is getting better, there is usually little motivation to jump ship. Even less so, if you have already jumped across the same ships in past. Some competition is, of course, always good to have and I am very happy to see both platforms evolving.