Gecko currently has much deeper integration of the XSLT engine with the browser internals: The XSLT engine operates on the browser DOM implementation. WebKit and Chromium integrate with libxslt in a way that's inherently bad for performance ( https://github.com/whatwg/html/issues/11578#issuecomment-321... )

Just Firefox XSLT is faster, better, cheaper than Google's (and JS), same, old Firefox extensions were to powerful Google could compete with Firefox (or block adblocks).

JS is very needed for ads, tracking and other strings attaching - and XSLT is not for that - but would make JS mostly obsolete in many cases.. [..]

Google pay Mozilla to criple Firefox. It's money from ads, to not let the web be free. Right now, how much $ and CPU power a JS engine could cost, for that, is irrelevant - except for the final user [paying for that saving on costs by some big company - or having to redo NOW in less efficient way something that still works well so far regardless of decades passed] !

https://news.ycombinator.com/item?id=44994459 - with answering lame questions of a developer not having a clue what is all about.

(Just.. live and let others live too ? Thx.)

Moreover.. Content First - and browser is a secondary thing to existing content (Chrome came after) - not the (double) opposite (primary, for ads n tracking instead)

- isn't Google as a public servant - so part of their job is to fix their bugs - but not in the position to decide to kill someone else existing content or solution - for not displaying ads so easy?