To chime in on this, pretty much every single thing you put to your mix bus and mix into, makes the final mix sounding worse when disabling it. Just put a simple EQ to your bus with a nice fletcher-munson on it and disable it when the mix is ready. Suddenly, your mix sounds boxy and dull without it. Does that mean that the simple EQ now magically become a godly new "betterizer" plugin?Mix into it from the start
Be it anything- a bus compressor, tape saturation or a simple EQ (or even more obvious, a stereo spreader), taking it suddenly away from the full mix makes it sound weird and bad while re-enabling gives you the impression that the plugin does wonders to the sound. It does, because you mixed into it and it was an integral part of the sound from the beginning. A well-thought "betterizer" is measured by how it betters your (almost) full mix.