This type of argument is especially frustrating because the whole post is essentially a strawman. The days for needing an engine team just to get your game working have been over since the ps360 days and some would argue much earlier. I don't see anyone in here making an argument that all teams should build their own engines or that it's a bad thing for teams to use 3rd party engines. Very confusing.
I think I can better position the counter argument. Imagine if the engine was a professional kitchen. And when we compare professional kitchens, they more or less have the same things in that kitchen.
But one kitchen uses Natural Gas stoves, and the other for some reason say uses induction.
But the kitchens have their own staff and their own menus, and we rate one restaurant's dishes as better than the others.
But instead of aligning the reason to the staff for coming up and executing on a better dish, we point at the gas vs induction as the reason for better dishes.
I think ultimately, the tools are out there for all engines, custom or 3rd party. The middleware is all out there too, to make any game. The problem isn't the kitchen or the equipment. The problem is the menu and the ability of the staff to execute on delivering that menu.
And while I agree technology does play a factor here and there, at the extreme edge cases - the majority of the failure that any kitchen (even the best ones) will succumb to, is being asked to cook their dishes correctly under a time constraint. I've been to the best restaurant that missed a few orders, and then started sending rush orders and salmon kept coming back undercooked, and then everyone elses dishes started getting undercooked, etc etc.
And games aren't any different. Most games coming out that fail to deliver is because they failed to cook their dish correctly. Something needed more time, and the pipeline of content was just not generated well resulting in terrible backorders etc. I think Bioware came up in this thread, and ME:A and Dragon Age II and Anthem were all cooked under 18 months. I know they complained about the engine, but that was just 1 more complication, on the reality that they had 18 months to make a product, because they spent 18 months earlier that work was tossed away.