Agreed, it's not very constructive feedback. Google does respond to feedback on the Issue Tracker, but I've found posts that sound like rants tend to get ignored (unless there's some critical issue at play).

It's also not a very constructive UI change, and the Pixel 6 doesn't allow rolling back to Android 12, so if you do update, your premium-priced phone suffers a UI downgrade. I don't think anger is unreasonable when all is said and done, it's a phone. It doesn't need constant screwing around with the UI, just make it secure, reliable, and optimize it.

It doesn’t matter if anger is at play. At the end of the day, if you want something changed, you should act in the best way to get it

The best way in 2022, sadly, if you have little clout, is to create a public outcry and potential PR disaster. See it every day on Twitter.

Yes, I'm explicitly asking them to undo their work because it was actively destructive for everyone's user experience.

Consider, maybe, the psycology of the interaction. You may well be used to direct feedback, but when driving change in another organisation -- especiallly one where it's really cheap for them to simply ignore you -- it can help to consider how people will react and make it as easy as possible for them to take the action you want them to.

We can assume that they made these changes deliberately. Therefore it's going to take a lot of conviincing to get them to undo the changes.

For what it's worth, too, I disagree with you: I'm quite happy with the asethetic they've built. Although, in case it's not clear to you, no-one outside of Google can see the screenshots you supplied. So I've not seen the specific notifications you're complaining about.

How not what is the problem.