1. Webapps are largely overloaded and dont need to be as huge/complicated as they are.
2. Webapps are an objective computing miracle that brings full app functionality to tech illiterate people that is platform agnostic, everywhere on the planet, and thus most of their complexity is justified.
3. Performance for performance sake is never a hill to die on as it always leads to increasing complexity.
4. Performance when performance matters, is invaluable, and you should be prepared to make dramatic concessions for it.
5. Chasing metrics where the value is not something you easily understand, is usually never worth it.
6. Chasing metrics whose value is obvious (for example, PageSpeed) is worth it.
When websites should be static, they should be static. When webapps should be webapps, they should be webapps.
Software is a tool. A means to an end. Getting hung up on things like this isnt worth it. Just focus on delivering value to your users, and making it a good experience. Sometimes thats best achieved through a static website, sometimes its through a webapp.