> the devs and other users keep telling me I shouldn't want that as a feature and that it "doesn't make sense"

I mean if the devs and the users are all telling you it doesn't make sense, maybe it really doesn't make sense. Not everything is supposed to be able to do everything. Some things are targeted and focused on specific use cases.

But surely even in a SPA you have to eventually send a request and get a response? Like you're not going to suggest that eg in an online store webapp the user would click 'add to cart' and you wouldn't send a request to add the item to the cart and wait for and render the response?

Hypermedia libraries like htmx etc. are just doing these interactions, the ones that need a server request-response cycle. The difference is they get the response as already-rendered HTML, so they don't need to do anything further, just swap it in to the existing page. It's super simple and very efficient. And usually results in fewer AJAX calls which also are much more minimal and don't include any redundant data.

> not to have to think about e.g. standing up a HA PostgreSQL cluster or Redis

I don't understand...Rails does not replace a HA PostgreSQL cluster or Redis, they are orthogonal. Why would you not have to think about them?

Yeah but the problem is that people don't just use a single webapp all the time. We all browse and go to many different websites, which all have payloads that they want us to download and run. So in practice it ends up that we're re-downloading bundles constantly, many of them which have the exact same libraries, but because they're bundled and minified, they're not cacheable so we have to fetch them over and over again.

Don't believe me? Check this out: https://tonsky.me/blog/js-bloat/

Actually... https://github.com/microsoft/TypeScript/issues/52924