To those disagreeing with Drew here: he’s expressing it very bluntly, but what he’s saying is absolutely correct. People keep on reimplementing what browsers already provide, and they seldom do a good job of it. In fact, often it’s impossible to do a flawless job of it—e.g. you can’t get a custom dropdown to behave (not look, behave) like a native <select> without some fairly detailed user-agent and platform matching (I mean things like whether selection is focus or not, and what Tab does when the dropdown is open and selection is not focus), quite apart from the other details that people often skip over (see https://www.w3.org/TR/wai-aria-practices/#Listbox for a summary); and scrolljacking is always bad because the primitives exposed are insufficient to reimplement scrollable areas.

This is an attitude problem with a large fraction of web developers that causes trouble for users. You should very strongly prefer to use a native element and technique for something if you can. And buttons… well, buttons are a great example of something fundamental that the browser has a good implementation of, which is often reimplemented annoyingly incorrectly.