Irrlicht had its editor (irrEdit), a sound system (irrKlang), and some basic collision detection and FPS controller was built right into the engine. This was enough to get you a considerable way through a fully featured tech demo, at the very least. (I even remember Irrlicht including a beautiful first-person tech demo of traversing a large BSP-partitioned castle level.)

However, for those not afraid to stitch these additional parts from other promising libraries (or derive them from first principles, as was fashionable), OGRE offered more raw rendering prowess: a working deferred shading system (this was the heyday of deferred shading), a pop-less terrain implementation with texture splatting, and more impressive shader and rendering pipeline support, with the Cg multi-platform shading language. I remember a fairly impressive ocean surface and Fresnel refraction/reflection demos from OGRE at the time.

"Ogre3d is a graphics engine, if you want to spend the time to strap a game to it, go for it."

The direction of dependency is from your program to the console specific stuff. You can write a platform library which is linked to your program without releasing that library.

> modern boomer shooters

I didn't say for boomer shooters. It's a general 3D game engine.

> just use Unity, Unreal or occasionally Godot instead of the actual Quake engine.

Because they are popular and familiar, not because they did a serious evaluation.

Also my comment was about Irrlicht/Ogre, etc.