If you really need to make a compromise with only one lens, Sony 20-70f4 seems to me as very interesting option to me. Not ideal for portrait, but nice for all other mentioned genres.
2 points:
"portrait" means many different ways to picture a person or even persons: head only, Head and shoulders, body, environmenatl portraiture, etc.. This includes numerous combinations of focal lengths and apertures to compose the shot. Some of these require "fast" lenses (not discussing DOF needed to get a whole face into DOF...), and most of the times lenses with smooth bokeh are favored for all good reasons to do so.
With that out of the way, and the OP asking for a compromise: If the choice for his single lens is the 20-70/4G, the choice should incororate info avaibable about its bokeh rendering compared to other lenses, and the "limits" of DOF control with a maximum aperture of 4. The educated buyer will then cater for the shot wanted by limiting the potential impact of what some consider as shortfall of the lens while incorporating its strengths (BTW, a recipe for all shots with any gear, there is no perfect gear kit going up to 11...)
I was asked by friends for portraits of their kids at home. In the shot below I tried to take all of the above into account - Environmental portrait with 20-70/4 - EXIF intact, shared at full size for pixel peeps:
Cheers,
Ralf