I disagree. An HTML website which uses links, forms, buttons and inputs will by default:

* Have working back/forward buttons * Have working progress indicator as provided by the browser * Show errors to the user - even if they are ugly * Be accessible to keyboard navigation

With SPAs these are all things the developer has to get right.

So often when using a SPA I'll click a button, you get a spinner and then nothing will happen. Is it still in progress? Don't know. Eventually I'll open developer console and trace the network requests to find the JSON HTTP request that returned "ERR_BAD_EMAIL" and fix what I've entered. With a normal form submission at least the user will see the error message and can press back and then fix it.