A lot of old games have become unplayable on modern hardware and operating systems. I wrote an article about how making games open source will keep them playable far into the future.
I also discuss how making games open source could be beneficial to developers and companies.
Feedback and constructive criticism are most welcome, and in keeping with the open source spirit, I will give you credit if I make any edits based on your feedback.
The engine Can of Duty uses is effectively a heavily modified quake 3 engine.
By this point it’s so modified it may as well be a different thing, but make no mistake it has evolved from the quake 3 engine.
Half-Life Alyx still has some flickering light code from the original Quake. Couldn’t find a good gif that would include Alyx, but here’s a couple other games:
The first 3 or 4 used quake 3 engine for sure, but didn’t they switch it at some point?
Edit: nm I found the wiki page on the topic: https://en.m.wikipedia.org/wiki/IW_(game_engine)
Tldr; it’s what you said