Rolling your own engine seems to become troublesome when you're moving into AA territory (Cyberpunk/RED, FFXIV/Luminous, etc).

I guess at the low end (indies), you can design something lean that fits one specific use-case, and at the high-end (AAA) you really can afford to build/maintain something competitive. The middle-ground might be dangerous.

That being said, there are literally dozens of abandoned game engines out there from solo "game devs" who never actually got around to making the game.