I was thinking that this was not quite correct as I saw the problem. A vanilla html-css-js page from 10 or 15 years ago will probably run just fine in a modern browser (though it will look its age). The loads of external dependancies is what will doom web projects.

A tweet down-thread coined a word for this:

Ry @RyanMorey I think we need a different term for this than bitrot. It’s not data corruption breaking these, but like compatibility corruption? PlatformRot