Yes, WebRender makes up the compositor portion of the browser rendering engine. A very large, critical portion of it. Thus, saying "Gecko had a good and honorable run" is disingenuous to the large-scale changes and progress the developers have made (and continue to make) on the rendering engine.
I think you think I hate Gecko. In fact, I've used it since it was NGLayout and think it's one of the most important pieces of software in computing history. I have deep respect for the world-class engineers working on WebRender and other Gecko components.
I simply think that it's time has come. Remember that Mozilla itself once intended to replace Gecko with Servo.
I have no doubt that WebRender is brilliant, but WebRender will not save Gecko, and Gecko will not save Firefox.
If Firefox is worth saving — and I think that with hard choices, its decline can be reversed — then Gecko and its components are non-differentiating ballast that must be dropped if the balloon is to get over the mountain. IMHO, of course.
