There are so many variables in an issue like this that one person's opinion is just that -- one person's opinion. So, FWIW, here is my opinion, which really only applies to my style and objective (and note that as I get older, weight is more of an issue).
With the wall display B&W landscape prints I target, sharpness does matter. So primes are my usual optics (though an outstanding superwide zoom -- Leica WATE for the Sony a7r -- was my last purchase). What I saw in my first (1981) one man show was people going up to my 35mm images to see the detail and then backing off because the detail was not there. I, personally, think that is a negative for landscape work. I switched to medium format film immediately, but have returned to full frame "35" -- enough is enough, and I got tired of dragging around too much heavy equipment. On the other hand, it's the composition that makes a shot great, and if you miss it because you're changing lenses, the additional detail of the prime will not help a bit.
While I want the sharpness to be throughout, it does seem to be true that people are much more forgiving of slight softness at the very corners and foreground, as long as those are not centers of interest. We are conditioned to this. So, for example, I often take a dual-focus shot with a non-tilt optic instead of using my tilt-shifts, and the distant focus is usually at the infinity stop (if the lens has one -- another issue that matters to me) because a sharp mountain ridge or distant detail is often where people will see the lack of sharpness most.
I sure wish my 24-105 L zoom was good enough (and lighter), but it's not for me unless I know I won't have the time to switch lenses and I know I'm going to need more than a single focal length.
Frankly, in recent years I've found I can do so much with just a 35mm lens, that I often go with just that on the camera when I know time is not going to allow switching. I'd rather have a few outstanding shots that are really sharp than more shots that are not quite up to what I personally appreciate the most. My #2 most important optic is a 75mm f/2.8, and it's not used that much. The ability so stitch makes the wider angle lenses much less important; whether my new superwide will end up being worth the weight (not to mention cost) is an open question.
Paul
www.PaulRoark.com