And it's a very weak defence. There are great rebuttals to whatever he writes in there.
I mean, he rants that HTML failed, and then literally proposes "By providing low-level primitives instead, applications could ship with their own implementations of high-level concepts like layout, widgets, and gestures, enabling a much richer set of interactions and custom experiences with much less effort on the part of the developer."
Has he tried to implement any of those from scratch using only low-level primitives? How is it "much less effort on the developer"?
In general it just reads like a justification for Flutter:
"This API alone is not useful for application developers, since it provides no high-level primitives. However, as with other platforms, powerful frameworks will be developed to target this set of APIs. A proof of concept already exists in Flutter"
Why not provide high-level powerful primitives out of the box? Oh, then Flutter wouldn't have a reason to exist.
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As a side note: WebHID is a Chrome-only non-standard. They literally dumped a non-spec onto other browser vendors, shipped it to prod, and then "updated" the spec later: https://github.com/mozilla/standards-positions/issues/459