That was exactly my experience few months ago when I was building a wysiwyg resume builder. The first problem I faced was that if I was entering some text and switched from the browser to another app and then back to browser, I would lose focus. So I had to built custom logic for that using a whole bunch of workarounds. But this was an even bigger pain because if the user's cursor was in the middle of a sentence and not at the very end, then placing the cursor at a specific position was quite complex in content editable. Similar problems if the user had selected/highlighted some text.

Undo/redo logic was another nightmare. And copy paste required a ton of clean up before.

Next issue I faced was that if the container element had certain css formatting applied (can't remember which one) then if I hit enter, then backspace won't work. If I remember right, this had something to do with a well reported bug related to pre-wrap, white-space, break-line etc. This was also when I discovered that the content editable would work differently across browsers. This was basically when I dumped content editable and went with a simple textarea and a "fake dummy" hidden textarea used for calculating the size, formatting etc.

https://resumetopdf.com/