What's the difference between influencing positions and visibility based on AMP support vs overall page performance?
If visibility is influenced by AMP then Google benefits, users using Google services likely benefit, web developers suffer, users not using Google services to view the content continue to suffer (because companies will continue to maintain two versions of the website, a bloated version with 100 external tracking requests that will be shared on twitter/reddit/facebook/hn/etc, and an AMP version that will only appear on Googles services), and the internet as a whole suffer. Whereas if visibility is influenced by page speed+external requests then everyone would benefit.
- AMP is a transparent and unambiguous standard that leaves no uncertainty as to whether you are somehow "performant enough" to qualify for the simple but limited visibility boost (referring to the news carousel)
- AMP prevents important usability problems beyond performance, like page content jumping
- AMP can enable advanced/extreme performance optimizations by default that are somewhat rare in practice (eg. only loading images above the fold) or isn't really possible to do safely/properly without a spec like AMP (eg. preloading content before the user clicks the link without unpredictably disrupting the website's servers) or sometimes avoided due to cost (eg. fast global caching with Google's impressive CDN). Important for users in the developing world.
Addressing your other points:
- Users who don't use Google services don't suffer. AMP is not Google-exclusive, all the major search engines (like Bing, Yahoo, Yandex) are stakeholders in the AMP standard and are free to support AMP. AFAIK there is nothing in the AMP standard that favors Google over other search engines or any other platform that might support AMP.
- Not sure how web developers suffer more from AMP. I'd think web developers would suffer more from trying to wrangle their bloated website performance independently rather than use a standard toolkit that enforces best practices and enables difficult/expensive optimizations out of the box.
- It's not clear to me how the internet as a whole will suffer, but I suspect this is just general hyperbole and not a specific point.
If visibility is influenced by AMP then Google benefits, users using Google services likely benefit, web developers suffer, users not using Google services to view the content continue to suffer (because companies will continue to maintain two versions of the website, a bloated version with 100 external tracking requests that will be shared on twitter/reddit/facebook/hn/etc, and an AMP version that will only appear on Googles services), and the internet as a whole suffer. Whereas if visibility is influenced by page speed+external requests then everyone would benefit.