Enough detail to clearly know what it's supposed to be. Not enough power to clutter things up and make visuals too busy. Stylization to work around the limitations.
Art tends to shine around limitations.
And just surreal, dreamlike enough to stoke the imagination.
I would kill for a youtube channel that just did nature documentary style panning shots over game scenery from this era with some appropriate music. Like how some games had level preview flybys, but slower.