The question is what exactly is needed for a useful and functional browser. You certainly don't need all features from Chrome, but you do need more than, say, Lynx or Dillo.

Is WebGL needed? I've browsed the web for years with it disabled and have not suffered any inconvenience. I'd probably say it's not needed, but I'm a bit on the fence about it and can understand if people would disagree. All browsers implement XSLT, but is that actually needed for a functional modern browser? Maybe not? I can't remember the last time I've seen it used, but perhaps it is. And do you include HTTP? Or is that too low-level? Do you include PNG and SVG or just PNG? If you include SVG then why not PNG?

There are some obvious "we need this", some obvious "we don't need this", and a lot of unclear and somewhat subjective area. I do know that you can't really say "yes there's bad data, but it probably cancels out against stuff omitted"; if anything, it only underscored my point that the list is not good.

An uncurated or minimally curated document dump is not the correct approach in the first place, if you do that for SMTP you'd end up with a lot of irrelevant documents too simply because the specification is a few decades old and stuff gets superseded, some things never sees real-world implementations, things no one uses any more, etc.

I started making a better list when the article was originally posted, starting from "okay, let's just check what you need for a useful browser normal people can use every day" and ended up with a few dozen things, but I never really posted it as I wasn't quite sure that was fully correct either and because I never really figured out some of the questions above.

I think most of the complexity stem not just from the word count, but rather that everything interacts with everything else. Consider the relatively new "position: sticky" in CSS. Okay, great. But it doesn't work well with flexboxes, or RTL, or negative margins, or z-index, etc. etc. [1] Adding what seems like a fairly simple feature is quite complex because it interacts with so many things. It's not hard to imagine a fresh new HTML and CSS which allows all the features the current does but does so in a much simpler and orthogonal way, which would of course break backward compatibility and every website.

[1]: In 2020 anyway; I'm not sure on the current state; here are some of the links of my post from 2020 which like most of my posts I never finished:

https://bugzilla.mozilla.org/show_bug.cgi?id=1488080
https://bugzilla.mozilla.org/show_bug.cgi?id=1498772
https://bugzilla.mozilla.org/show_bug.cgi?id=1519600
https://bugzilla.mozilla.org/show_bug.cgi?id=1490487
https://bugzilla.mozilla.org/show_bug.cgi?id=1488950
https://bugzilla.mozilla.org/show_bug.cgi?id=1514291
https://bugzilla.mozilla.org/show_bug.cgi?id=1528957
https://bugzilla.mozilla.org/show_bug.cgi?id=1472602
https://bugzilla.mozilla.org/show_bug.cgi?id=1455660
https://bugzilla.mozilla.org/show_bug.cgi?id=1450601
https://bugzilla.mozilla.org/show_bug.cgi?id=1424384
https://bugzilla.mozilla.org/show_bug.cgi?id=1341643
https://bugzilla.mozilla.org/show_bug.cgi?id=1526342
https://bugzilla.mozilla.org/show_bug.cgi?id=1519073
https://bugzilla.mozilla.org/show_bug.cgi?id=1414874