Insofar as that's true, the question becomes, "who defines function?" Web developers will tell you they do, as if that's a stupid question. But the developers have little interest in empowering their users. In the best case, they want predictable uniformity, where a user can't do anything they haven't defined in advance and thoroughly tested. It's not (always) malicious, but it is certainly constraining.
The web we have now is the web that 90s applications developers insisted that everyone wanted:
* the site needs to be able to enforce content protections
* the site needs dynamic UI elements to hide unnecessary interfaces and un-hide them once they become necessary
* the site needs to control the loading of content to minimize stress on the servers and network bandwidth.
* the site needs to be tailored to each user.
* the site needs to be stateful
* the site needs to offer a uniform experience on all platforms
* platforms which cannot comply must be locked out.
* though not a stated goal, all these new features require a lot of new markup.
In other words, web pages today strive to be something you could run on Windows 95. And that runs completely contrary to many of the design decisions that built the web, and gave the user power.
* before dynamic UI elements, the browser could process data as the user wished. You could search a page for text knowing it wasn't "there but hidden", because there was no such thing as hidden. there wasn't even "on this page, but not loaded yet". You could scrape an entire screen easily.
* A file or site was either live, or not. Passwords, aside it wasn't generally something that was going to become inaccessible or disappear. It certainly wasn't going to be different for different users. This "unstated feature" was one of the first things to go, because it doesn't depend on the nature of the web so much as the hosting and retention goals of the site's owner. Even so, for about a decade very little disappeared from the web unless and entire company went down.
* It is difficult to the point of foolishness for an inexperienced human to design a modern-ish "web app". The human-readable content of a modern site is a trivial portion of the underlying code. Participation is generally one-way, unless a user signs up with some sort of broker (like Disqus) to host comments which can be drafted with an exteremely simplified mark-up and decorated automatically.
As the sites grow in power, the browser and the users diminish.