If you devote yourself to developing one character or another intimately, and with devotion, it's always going to be a self-insert to an extent. Because let's be realistic, where do these characteristics come from if not some part of yourself. You need to empathize with your creation on a significant level to be able to breathe life into them. If they weren't a part of you before, they become as such through the whole process. Unless they're on the other end of the spectrum, i.e carbon copies of other fictional characters.