Honestly, the single biggest issue with the engine sounds in the game is that they're just too quiet. The wrong samples aside, if they just mixed the engines louder or more forward in the soundscape, it'll stop most of the "the engine sounds are trash" complaints. Raising the volume is the easiest way to enhance perceived audio quality.
Right now, it just feels wrong that the music can almost completely drown out the sound of the cars in chase cam even when the radio slider is set to 1. Timeless is probably the worst because classicals get loud.
And before any "just get better speakers," I can safely say that I have an equal, if not better, nearfield setup to most recording studios. So no, that's not the limiting factor here.