> But wasn't this the promise with JavaScript already, a Turing-complete language in the browser to end the need for more features of HTML?
The problem is javascript sucks. We want to be able to write any kind of application, but we don't want to have to do it in javascript. Ideally, this would mean that you pick Java or C# instead and use one of several cross-platform UI frameworks, but I've never found a native UI framework that was as easy to work with as HTML. If C# would just let us write native UI with HTML and CSS (and not just using electron), then I would never write a webapp again
> We want to be able to write any kind of application, but we don't want to have to do it in javascript.
To make "any kind of application" on the web you need the web to provide sensible APIs for those applications. And Javascript has nothing to do with it. E.g. lack of controls listed over at https://open-ui.org/ has nothing to do with Javascript.
> If C# would just let us write native UI with HTML and CSS
Good luck implementing anything beyond the most basic controls with HTML and CSS.
I don't think so, no, or rather, I think you might lose out on "the web" part of it. That is, that the web really is a bunch of stuff, all accessible in one "thing", and stuff can and does "link" to various other stuff.
E.g., consider an OIDC log in. It's really one app (the relying party), redirecting to a whole different app (your SSO of choice). You can't exactly do that in another app without, I think, really running into issues of "is it my SSO, or a phish?". The browser provides that trusted layer of "I am look at this app" (via the URL bar). And even then … that's fraught with absolutely immense tons of peril.
It's also a distribution mechanism: I don't have to download Slack, Discord, Postman, etc. — I just go to a URL, and the browser downloads the code needed. (I can and do download some of these, and there are some advantages to do so. But then extend it to every app I use on the web: my bank, Turbotax, my email, my three different loan payment sites, my landlord's payment site … that'd be far too many downloads.)
The problem is javascript sucks. We want to be able to write any kind of application, but we don't want to have to do it in javascript. Ideally, this would mean that you pick Java or C# instead and use one of several cross-platform UI frameworks, but I've never found a native UI framework that was as easy to work with as HTML. If C# would just let us write native UI with HTML and CSS (and not just using electron), then I would never write a webapp again