"it gets easier and more mandatory to do more in Javascript and harder and more expensive to fake the presence of comparable functionality using HTML, forms, etc."

You don't have to "fake the presence of comparable functionality" (and in most cases you simply can't).

What you can and should do is support the subset of functionality raw HTML and CSS sans Javascript can achieve. No one will blame you for not supporting highly dynamic features that can't possibly be achieved without javascript without javascript.