Infocom, Sierra, and LucasArts all built proprietary VMs and it seems to have worked out very well for them. People are still making new games that run on Infoc

Infocom, Sierra, and LucasArts all built proprietary VMs and it seems to have worked out very well for them. People are still making new games that run on Infocom's Z-Machine, and ScummVM has helped keep those LucasArts games running to the modern day. Unreal Engine was very successful with a custom scripting language up until UE4, too. And Naughty Dog hardly seems to have suffered from their decision to build a Lisp-based system -- apparently they're still using Racket to script their (wildly successful) games. Really, it's only quite recently that the off-the-shelf tooling like UE4 or Unity has gotten sophisticated and powerful enough that people can make complex games without having to build a little software ecosystem around them.