Where are you seeing that it’s a single website? Mootools is a JavaScript library used by tons of websites.
Also, the entire measurement is fundamentally just part of the decision. Removing Flash broke tons of sites, and it was done anyways because Flash was a nightmare.
> Existing content often relies upon expected user agent processing and behavior to function as intended. Processing requirements should be specified to ensure that user agents implementing this specification will be able to handle most existing content. In particular, it should be possible to process existing HTML documents as HTML 5 and get results that are compatible with the existing expectations of users and authors, based on the behavior of existing browsers. It should be made possible, though not necessarily required, to do this without mode switching.
> Content relying on existing browser behavior can take many forms. It may rely on elements, attributes or APIs that are part of earlier HTML specifications, but not part of HTML 5, or on features that are entirely proprietary. It may depend on specific error handling rules. In rare cases, it may depend on a feature from earlier HTML specifications not being implemented as specified
Which is the "servant-oriented" mindset I'm talking about here.
> Removing Flash broke tons of sites
Yes, but Flash wasn't part of a standard, it was an ad-hoc thing that each browser _happened_ to support (rough consensus and working code). There were no "build on this and we'll guarantee it will continue to work" agreement between authors and implementers of the web. XSLT 1.0, as painful as it is, is part of that agreement.
I think you’re pretty off-base about how web standards work and how much of an “agreement” they constitute.
Flash doesn’t have an RFC because it was a commercial design by Adobe, not because it wasn’t a defined spec that was supported by browsers.
Meanwhile SSLv2 and v3 and FTP and gopher have RFCs and have been removed.
Making an RFC about a technology is not a commitment of any kind to support it for any length of time.
You’ve conjured a mystique around historical browser ideology that doesn’t exist, and that’s why what you’re seeing today that feel at odds with that fantasy.
Flash was a plugin to the browser ecosystem that no one ever made a commitment to other than "here it is".
SSLv2 and v3 all are protocol versions that anyone can still support, and removing support for them breaks certain web properties. This is less of a problem because the implementations of the protocol are themselves time-limited (you can't get an SSL certificate that is valid until the heat death of the universe).
FTP and gopher support wasn't removed from the browser without a redirect (you can install an FTP client or a Gopher client and the browser will still route-out-to-it).
The point isn't "RFC = commitment", the point is that "the culture of the web" has, for a very long time, been "keep things working for the users" and doing something like removing built-in FTP support was something that was a _long_ time in coming. Whereas, as I understand it, there is a perfectly valid way forward for continuing to support this tech as-is in a secure manner (WASM-up-the-existing-lib) and instead of doing that, improving security for everyone and keeping older parts of the web online, the developers of the browsers have decided that "extra work" of writing that one-time integration and keeping it working in perpetuity is too burdensome for _them_. It feels like what is being said by the browser teams is, "Yes, broken websites are bad for end users, yes, there are more end users than developers, yes, those users are less technical and therefore likely are going to loose access to goods they previously had ... but c'est la vie. Use {Dusk, Temple}OS if you don't want the deal altered any further." And I object to what I perceive as a lack of consideration of those who use the web. Who are the people that we serve.
Also, the entire measurement is fundamentally just part of the decision. Removing Flash broke tons of sites, and it was done anyways because Flash was a nightmare.