I've spent time studying the source codes of various projects both to learn about their architecture and learn more about CS as a subject. I took a lot of inspiration from some of the high-level software engineering principles that Id Software always exemplified.

Ease of moddability, robust developer tools, and KISS make projects easier to understand and create with, which is what made games like Doom and Quake so prolific as modding platforms for so long (aside from their popularity and cultural impact).

As a prospective game engine architect, the results of their methods are appealing: the creativity enabled by a quality platform leads to an active and dedicated community with a high output of (hopefully completed) projects. I really want to develop a modular and well-documented architecture with an emphasis on planning and attention to detail on my end.