[gambiting]

I'd like to point out that I work at one of the largest(if not the largest) gamedev company in the world and 100% of our projects use our own engines.

Unless you believe that every single game should write its own engine from scratch, then I don't know what to say about that, it's just extremely obvious that it's not feasible for every project regardless of whether you have 100 or 10000 people working at your company.