Well, the statement that "resolution is of utmost importance for landscape photography" is questionable in itself. As far as I'm concerned, the highest priority in photography is taking a great photo, so composition and timing are of the utmost importance.

However, high resolution is always good. For landscape photography, you pretty much nailed the reasons why in your first three points (the third one being similar to the first).

• Enlargements! Landscapes lend themselves well to being blown up large and hung on the wall; at least, many people feel this way.

• Landscapes capture detail that stretches far off into the distance, as well as detail that is closer. The more resolution, the more detail a close viewer can see on the horizon if they look closely enough.

However, the statement might appear to imply that resolution is only important for landscape photography, or that other forms of photography don't require as much resolution. This is wrong. Other types of photography can benefit from high resolution, too. For example, high resolution portraiture captures better texture and detail in clothes and hair.

As to your possible problems:

Often the subjects are naturally occurring, making distortion difficult to spot imperfections

Low resolution doesn't cause distortion, it causes lack of detail. Lack of detail will mean that distant objects on the horizon will be less distinct, or that very small objects or fine texture will be less distinct, along with the edges of objects.

Interpolation of features such as a sky I would think would be easier than a human eye in a portrait for example

The sky usually isn't what would benefit most from higher resolution - unless there is a lot of detail in it (what we call a "spectacular sky").

If a image will be enlarged significantly, typically it will be viewed at a corresponding further distance, negating the necessity for additional resolution

This isn't necessarily always the case. How often do you see a photo in a gallery and peer at it to get a closer look?

I am wondering if this might be a somewhat dated stance, considering what type of detail and resolution can be captured with basically any current DSLR. Maybe this theory comes from 35mm film days and no longer applies

It's certainly true that sensor resolution of new DSLRs has reached a point where you don't need to worry about it more than other things. 12 megapixels is pretty low end these days, and yet it is more than enough for a pretty high resolution image. There's also the resolution of the lens and of the output medium to worry about, though. It's no good having a 36 megapixel sensor if your lens won't resolve that kind of resolution or you print it using a 150 dpi process. So, sensor resolution is only one part of makes up the achievable final resolution of a photo, and you are correct that in some cases it's not the main limiting factor. It would be wrong to assume however, that it doesn't matter at all.