There are. You can make a complex JS browser application that's completely accessible if you follow every single recommendation, and ARIA-tag every element that needs it.
That said, a lot of what you are doing in a browser application is re-implementing your own version of stuff that the browser already does, and the browser's version of it is accessible by default. So a JS-free application is almost always fully accessible for no extra development cost (as long as you check it for things like foreground/background contrast).
That said, a lot of what you are doing in a browser application is re-implementing your own version of stuff that the browser already does, and the browser's version of it is accessible by default. So a JS-free application is almost always fully accessible for no extra development cost (as long as you check it for things like foreground/background contrast).