> Half-life was amazing, and not because it was Quake 2.

Half-Life used the GoldSrc engine [0], based mostly on Quake 1 and also some parts of QuakeWorld and Quake 2

[0] - https://en.wikipedia.org/wiki/GoldSrc

It was just called the Half-Life engine then. It was developed in parallel with Q2, and in general has feature parity with Q2, with a few huge features that they were able to add because of the extra year of development like skeletal animation.

Which is why I mentioned it. The engine itself was a copy pasta blend of idTech stuff with their own architecture.