I know that comparing lenses is a subjective and often futile effort, but I hope that if I convey my priorities and current understanding (as a relative beginner), I can still gain a lot of insight from your takes and opinions.
I currently own a Nikon D500 and the one lens I have for it is the Nikon 16-80 mm f/2.8-4E ED VR. I've found it mostly suits my needs as someone who mostly prefers to (casually) do portrait, group portrait, urban, and travel photography.
Since most of what I do is covered by the 16-80 mm range, I'm having a hard time figuring out what lens would be a significant contribution to what my current lens already does. It seems to me that at an amateur level the most significant upgrade in a lens that's worth shelling $$ on is going for a faster lens.
So I've started testing out the Nikon 50 mm f/1.8G and although I'm a fan of the results it produces, I'm not sure if I'm just convincing myself they're actually better, as on paper the DOF for the two lenses are pretty similar. The actual comparison of DOF at 5 meters is:
Prime 50 mm: .71m
Zoom @50 mm: 1.5m
Zoom @80 mm: .62m
Now here comes the really subjective part: with this 2x decrease in DOF at 50 mm being the seemingly sole contribution of this lens, is it the "best" next addition, or would I better off (with some difficulty) paying double for the Nikon 50 mm 1.4/g or going for something else entirely?