But that side project was an app, I presume? The web is not an application platform per se. Web content should be rendered as transparently and accessibly as possible. Just imagine a world where you can't use browser extensions, screen readers, even text selection...
To note, you can use flutter/dart and just have a web output (which works still fairly bad tho, last I checked).
It may not have been envisioned as one, but it certainly _is_ an application platform today. It's arguably the most popular most accessible application platform today.
Flutter uses a canvas rendering strategy where it’s painting all controls itself, so it’s not “native” in that it’s using controls from the OS, and therefore all a11y and select functionality is implemented custom.
That really depends heavily on the platform and specific app. It is not there by default for most. Using canvas based rendering is pretty much as accessible as flash apps where, which is not much by default.
