After reading some comments here I come to the conclusion that (too) many web developers are just a bunch of opportunistic ignorant hypocrites. On the one hand they repeatedly state that constantly expanding variety of HTML9 technologies[1] is THE best thing that could have ever happen to the Internet and that there is nothing worse than mono culture . On the other hand they do not seem to be willing to even consider…
But if you open your mind a little, you'll also see that the two opinions can also be totally compatible, just dependent on the context. For example, expanding "HTML9" (ha!) can be great for exploring, prototyping, experimenting, where a monoculture is bad and harms innovation. While only >10%-share browsers can be worth commercially developing for, because of resource constraints.
In other words, ideally, there would be a "polyculture" in innovation and experimentation, that would constantly funnel into a "monoculture" in actual final standards. Of course, that's hard to establish and maintain in practice, but you can see how they're just different perspectives.