This is a somewhat naive view of engines in modern game development. Full-featured engines allow every department to dive in head first in parallel. The first gameplay elements often get programmed before the first pieces of content arrive. Scenes can be blocked out and drafted immwdiately at the start of the project. Complex animations with states and blend trees can be created amd tested independently of the gameplay code. Audio scenes, complex cues and (dynamic) music can be mixed and mastered independently of any code to integrate audio into the game. The whole process is highly parallelized these days and the engine tools serve to insulate the departments from one another to some extent so that everybody can move faster.
Right, yes. I think all I meant is that in earlier generations you could do modeling/sprites and concepting from the beginning, but there was a hard line in terms of how much code had to exist before the whole thing started to look or feel like much.
Thinking here especially of the Doom / Quake / HL1 era where they were basically building the level design tools in parallel with the game.
Whereas nowadays you can have movement, mobs, dialog flow, etc all with very little code, and it's placeholders like "oh we need a custom shader for this effect" or "that boss needs some custom logic".