I keep hearing this, but I think it's too broad of a statement.

There are definitely functionalities that are impractical to implement with server-side rendering and forms alone. Map widgets and drag-and-drop come to mind.

The issue I have though, is that the overwelming majority of web functionality can be implemented as server-side rendering.

Even HN would have a poor usability with only server side rendering.

But you don't need javascript frameworks to add a small amount of state changes without page reloads, it's very easy to do without using something like react.

The comparison is between server-side with a bit of js where required, and the proposed 'modern web' where js frameworks attempt to take over the entire experience server and client side so that they can remodel the world in their image.

Most websites simply don't need react and friends, even if they are more app-like than doc-based they still don't need it, and they certainly don't need to be a single page application (the best modern example of throwing out almost everything that is good about the web - urls, links, docs, stateless).

Turn javascript off and find out. The only difference I know of is that the vote buttons force a full refresh instead of making an ajax request.

Sure, but it's much leaner because it only uses JavaScript when it is necessary.