I'm not commenting on "ethics", but I can say why I dislike AMP as a user: I want to interact directly with a website, not through some third party. I especially don't want that third party observing my interactions or collecting data about them. I also don't want to allow that third party to run code (javascript) on my computer.

As a website designer (barely), basically the same reasons: I don't want my site under control of a third party, I don't want my users to have to run javascript to view my site, and I don't want them to have to consent to (possibly) being tracked. Most ironically, my site probably accomplishes more of the stated AMP goals (due to being pure html and light) than it would when AMPed up.

Quick edit: I also worry it can contribute to breaking or obfuscating hyperlinks, which is similar to the issue raised in this article. Having hyperlinks work correctly is crucial to the design of the web. I had similar problems when sites like Google search started making their search links redirect to some intermediate site before going to the actual link, and back when I used Google search I had an extension that removed them so I could e.g. right-click and copy the link.