For those who've switched over to Firefox recently and find Youtube inexplicably slow, it's "because YouTube's Polymer redesign relies on the deprecated Shadow DOM v0 API only implemented in Chrome." [0]
I'm on the Polymer team at Google. We've been helping the YouTube team, who's been doing a ton of work to update to the final v1 version of the webcomponent specs. So far it's a bit neck and neck between Firefox launching version 63 with native web component support (eta October) and YouTube switching the main desktop app over.
These are new standards, and there were a number of breaking changes from the v0 specs to v1. It's a lot of code to update, but we're working super hard to get all of Google onto v1.
fwiw if you read the rest of that thread on Twitter it explains that Youtube is not using Shadow DOM v0, the slowness is likely related to polyfills for HTML Imports, and the next version of Polymer no longer uses those to resolve issues like this.
Microsoft left IE6 stagnant. They didn't "abuse their position" other than through inactivity.
Google is actively involved in the standardization process, and moved Youtube over to a new API too prematurely (v0 of a spec). Now that v1 has been standardized, they're updating to that instead.
These are opposite problems. Microsoft got complacent whereas Google moved too fast.
It's more of an OS issue here. Google doesn't view Android as a separate line of business. It's merely a moat for the search business. There's no way for an OS to be a moat for another business without abusing the OS.
Oddly enough I haven't had too many issues with YouTube's slowness (as a Firefox user). I mean, it's slow, but "tolerable". It's the new Gmail that's horrifically slow now. It takes a good 20 seconds to get to the point where I can interact with it, and then each interaction takes another 10 seconds.
I mean, polymer also broke most of the chromecast functionality in google's own browser to the point that I have to use ?disable_polymer=1 to really use it at all from a browser (really I mostly just use it from my phone now), so this doesn't seem terribly surprising by comparison.
These are new standards, and there were a number of breaking changes from the v0 specs to v1. It's a lot of code to update, but we're working super hard to get all of Google onto v1.