Note sure, but doesn't AMP have "custom elements" which are not just CustomElement+Shadow DOM but google pseudo-proprietary "pre-loaded/created" elements?
Anyway it's nevertheless troublesome that google has so much influence that they can just push new web features without much discussion of other developers/browser vendors. Due to differences in internal design some features can be simple to implement for google but hard for everyone else (or the other way around, in which case google can just reject them by simply not implementing them).
EDIT: Also the non-JS web is basically dead. People should to come and accept that even if it's not perfect.
Anyway it's nevertheless troublesome that google has so much influence that they can just push new web features without much discussion of other developers/browser vendors. Due to differences in internal design some features can be simple to implement for google but hard for everyone else (or the other way around, in which case google can just reject them by simply not implementing them).
EDIT: Also the non-JS web is basically dead. People should to come and accept that even if it's not perfect.