Thank you @yannis7; I really appreciate it.
You are 100% right; we believe that it is super important that non-developers are able to achieve all the important aspects that are required to succeed as web creators. Performance is one of those aspects and it is very challenging for everyone, but especially for non-developers to have a shot to achieve the levels of performance required. Our work on AMP is exactly related to this. We want to make high performance, via AMP and the AMP plugin, reachable by anyone regardless of technical expertise or resources available.
The reason why custom JS is not allowed by AMP is that it is one of the main reasons for poor performance on the web. The ecosystem has been moving steadily, albeit slowly, towards more AMP compatibility, but there is still a long way to go. This page lists some of the known themes and plugins that are AMP compatible: https://amp-wp.org/ecosystem/
In principle, it is possible to assemble a full site that is AMP compatible if you use a theme that is AMP compatible, and plugins that are also AMP compatible. This page lists sites that are using the plugin in this way: https://amp-wp.org/showcases/
To conclude, thanks for your feedback and for expressing the need that is so important for the web. We will continue our work on making more and more components AMP compatible and move towards making the experience frictionless for both developers and non-developers alike.