My point is that the defensive stance shows that many developers want to work on custom engines despite other factors and that is driven by personal preference

My point is that the defensive stance shows that many developers want to work on custom engines despite other factors and that is driven by personal preference rather than any sort of cost/benefit calculation. And it makes perfect sense and you see it all the time in other fields too with people switching companies and/or start (side)projects so that they can work with specific frameworks, languages, etc.