Earlier quoted context omitted.
These days it's easier to create an OS from scratch than a web browser.
Lately I was tryong to understand the exact reason "why". Why are modern browsers so ridiculously complicated? Rendering a (albeit confusing) content is a PDF-like kind of job (or am I wrong?) What is the exact complexity here (except for JS compiler, which is again just a compiler)?
There are hundreds of standards spanning thens of thousands of pages. Some of them are obsolete, some of them are not, most of them interact with each other in complex and non-obvious ways.
An attempt to measure the scope is here: https://drewdevault.com/2020/03/18/Reckless-limitless-scope....
And that's before we get to things like Javascript or WASM.
Another measure is the count of WebAPIs. A modern browser ships six to seven thousand APIs: https://web-confluence.appspot.com/#!/confluence All these APIs are available via Javascript