so you agree then that no professional game developer should make their own engine right? because their job is to ship a product.
Craft > sales. Great craftsmanship always sells, so in the long run it is not a bad investment.
If your goal is to sell a game in 3 months, sure, but not even Unreal Engine will magically turn a rushed game into a good product.
90% of the development time is making a fun game in the first place, and you’re on your own there.
I mean there's a point when you can go "why bother selling a game when i can learn to algo trade and maybe get hired by a major investment bank" if you really want to push the logic of all money no creativity to its inevitable end point. There would be no gaming industry. There would be no art. There would be no music. There would be no sports. There would be no movies. All of that is wasted profit potential against simply being involved directly in finance and in trading assets, preferably rooted in underlying material commodities.
The framing of "a professional game developer.. job is to ship a product" is very indie. Places like ID, Bethesda, Volition (RIP) etc.: like a hundred people worked on the product and many did not own shipping the product. When you have tech team of 10 - 30 people whether you should make your own engine was more of a question. Lots of very popular games are made on their own tech.
Also, like what do you mean by engine? Minecraft was made with LWJGL.