Often a proposal is just that - someone trying to solve a problem by proposing technical means to address it. Having a proposal sent out to public forums doesn't necessarily imply that the sender's employer is determined on pushing that proposal as is.
It also doesn't mean that the proposal is "done" and the proposal authors won't appreciate constructive suggestions for improvement.
[Be the signal, not the noise]
In cases where controversial browser proposals (or lack of adoption for features folks want, which is a related, but different, subject), it's not uncommon to see issues with dozens or even hundreds of comments from presumably well-intentioned folks, trying to influence the team working on the feature to change their minds.
In the many years I've been working on the web platform, I've yet to see this work. Not even once.