A website is nothing like a book in form, function, purpose, appearance, use, lifespan, the list goes on.
You're confusing the equivalence. A "novel" is a type of book. A "website" is not a type of "something".
A website can be anything the owner wants it to be, with different functions and purpose. It doesn't need to conform to the other "novels" because of some perceived "effective form". That's the point I take from the OP's article.
Websites have not "found their form", that's just the reason you've chosen to believe based on so many websites using the same template.
A website can indeed be many different things, but a lot of websites have very similar purposes, so it makes every kind of sense that websites with the same purposes end up looking similar. Just like cars look alike. Or houses.
Of course websites with a different purpose are going to look very different.
I'm sure there will be improvements on that form in the future, but when that happens, most websites will adopt it, and most websites will still look very similar.