I wonder when was the last time that you visited Slovenia for geocaching? While it is true that there are a couple of power trails (and far too many for my taste, I haven't done a single one), especially in the east part of the country, they are easily recognisable and avoidable. Still, the number of power trails is far less than for example in Austria or Hungary. Mass geocaching has not ruined it as much as in some other European countries (and we recognise the problem and are actively promoting the concept of geocaching for quality not numbers).
First part is true, but the second part is largely wrong. Yes, once you get out of urban areas, the caches are (luckily, remember what you said about mass geocaching) not as numerous anymore, but most are well worth a visit and many are of exceptional quality both in terms of location and geocaching experience. There is only a handful of surviving geocaches by foreign owners and most caches that you will find in "very beautiful areas" are locally owned and fairly well maintained. Drop me a note next time you plan to visit the country, I'd be glad to provide you with some geocaches to spend your favourites on...
As for the tourists: yes, Croatia, Italy and Greece do get much larger number of tourists than Slovenia, so I quite agree that it was probably what was driving the selection for souvenirs. However, if you weigh the finds data with international tourist arrivals, you get a different picture: considerably larger proportion of foreign tourists decides to do geocaching while visiting Slovenia than for example while visiting Croatia. It's a curse of a small country, we simply don't provide enough in absolute numbers of whatever (caches, finds, visits, revenue) to be noticed easily from Pacific Northwest. Even though we are lively caching community and just below Top 10 of EU countries on every measure that you take. I think Estonia was overlooked in much the same way.