There are no more websites. There are applications, delivered on applications platforms, using css, html, and js as programming languages. Chrome is the application platform, and Google is the company shipping it. Like all application platforms, the interests of company who designs it always come first.
Let us return to a moment to the WWW's ripe vintage of 1995, when Netscape Communications Corporation released a browser which had 3/4 of the browser market share within a year of release. Their product was advertised as a consistent universal interface to the web. They created custom features for their product, such as SSL, and JavaScript. But many of the features were released to outdo its main competitor, Microsoft, who could dedicate far more resources to development (they had so much cash they didn't even need to charge for the browser!).
Netscape Communicator attempted to be a groupware solution combining multiple products to provide a complete solution for office and enterprise needs. But the design was too monolithic and complicated, and development was eventually halted. Ever since then, many organizations have attempted to build complete groupware solutions, but have been weighed down by the difficulty of developing such a complex suite of applications.
And so came the future. As the web's technologies progressed, so did the capability of content delivered through a "standard" web browser. Even though browsers have traded back and forth over who supports what, most of the time the browser with the majority market share holds all the cards. As long as that browser works the same on multiple platforms, they don't need to worry about cross-browser compatibility, because that isn't their goal. Netscape's original goal was to kill Mosaic, and they did that in spades.
Today, Google provides a mostly-complete groupware solution, delivered on its favorite application platform: its own web browser. The costs of developing and shipping the software to end users are much lower than traditional native apps, and they increasingly control more and more of the pipeline, even to the actual computer (Chromebooks are designed to cement Google's ownership of computing resources, freeing them from the constraints of other vendors' platforms).
They not only don't want you to have "less JS and simpler JS on a website", they don't want you to run a website. They want you to provide an application which runs on their application platform. In service of that goal, they have developed dozens of web technologies designed to further their own application platform, just like the Netscape of old. If they have to break compatibility with other browsers to do it, that's fine with them.
The bizarre thing is breaking existing websites on their own browser. If you can't browse the web reliably you'll stop using their browser, and then their app platform and apps are in danger of becoming obsolete.