When I look at many classic landscape photographs, I see notations such as "f/32" or "f/45" for film based prints. Down to almost pin-hole size openings, depth of field is huge and detail sharp.
There are two other issues that come up in large format that you will not always see in a digital SLR. The first one is size of image circle and movements. For example, a lens may just barely cover a sheet of 4x5 film without movements, but stop it down to say F22, and the image circle increases a wee bit, so you are able to use more movements. This is true for some, but not always all large format lenses.
Secondly - and i don't know why - on 4x5 film, the 210mm lens for years was the "standard". Especially in some photography schools. For example, my local community college photography course, the large format section they always sent out students with 210mm lenses. On 4x5, a 150mm lens is roughly the same as 50mm lens on 35mm film or a full frame DSLR. So 210mm is kinda like a 85mm lens - a short telephoto with shallow depth of field. So to get a full depth of field you are pretty much forced in to F22 or more. Especially if you are into tilting and/or shifting a lens, stopping down is often the way to go.
I guess that's where that old saying in large format come from : "F64 and just be there".
On a DSLR, especially wide angle lenses, even when I want good depth of field, personally I seldom find the need to go past F8. I usually make that my concern first - what I want the final image to look like, and I worry about lens diffraction, etc, last. For example, one of my personal favourite photographs I shoot was of a creek on the family farm in infra-red film, 35mm HIE. That old stuff form Kodak had grain the size of small pebbles.
Enlarged to 11x14" print, man it was anything but full of fine detail. But the coarse look combined with the infra-red gave it a really dreamy, surrealistic look that I personally liked.
So sometimes it's more important to get how you want the image to look, and worry about the effects of diffraction, pixel size, etc, secondly.