"They see it as an effective pursuit of knowledge."

Well, maybe that's their public standpoint. But it's value they bang on about on their forums and magazines.
Whereas, in the whole history of the ModAnt forum, the word "value" has only been used 113 times, and those probably weren't about monetary value.

"Another thing to think about is the picture outside the UK, where forms of treasure hunting similar to antiquarianism are no doubt still be taking place."

Although one form of it (metal detecting) is legal here, and mostly not abroad. We're almost unique in having continued to allow all the worst aspects of old-style antiquarianism. ModAnts on the other hand have preserved all it's best strands.