It is easy to criticize, but what is the solution? Is it even a problem? It is up to Iceland to decide what is best for them. Who are we (collective we) to complain that people go in large numbers to visit beautiful places?
It is impossible to "hide" these beautiful places anymore, the trend goes like this:
1. Beautiful place only known to locals;
2. A few visitors show up, and spread the word
3. Many more people come, and the place loses its "character". Most folks with kids and family can only travel during July and August, due to school holidays.
I have seen this happening in many places in my country, Portugal. Take the SW coast of Portugal, for example; a place I have known for 40 years. Some beaches and places are crowded in the summer, impossible to deal with. Most recent example is the Azores; last year I climbed Pico mountain, the number of people going up everyday is over 100 now... there are now cheap flights to Sao Miguel and Terceira islands, so the "invading hordes" are descending and, well, invading. Lisbon is becoming unbearable, apparently it is a hot spot these days, with many foreigners buying/renting houses in the historical centre of town.
I don't like it, but I can not criticize, as the income is necessary to the country. But it needs to be sustainable and planned, otherwise all goes to s*hit.