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.