I wouldn’t call FTP part of the web platform—it was never
integrated. All you could do was link to it, and then the browser might be able to render it itself (Firefox and Chromium, until a few years ago), or open another app that could (IE and Safari, and Firefox and Chromium probably can still).
JavaScript has added things, not removed them.
There are other HTML elements and attributes that were never in any spec and were supported by only some browsers, which are no longer supported (either it was IE, or the feature was removed), and explicitly described as obsolete in the HTML Standard. But they were never supported by more than two of the three or four main engines, or if they were their functionality has been retained.
So, if you have anything that has actually been removed from the web platform, please be more specific.
JavaScript has added things, not removed them.
There are other HTML elements and attributes that were never in any spec and were supported by only some browsers, which are no longer supported (either it was IE, or the feature was removed), and explicitly described as obsolete in the HTML Standard. But they were never supported by more than two of the three or four main engines, or if they were their functionality has been retained.
So, if you have anything that has actually been removed from the web platform, please be more specific.