At least for me, I feel a difference between tourism, and over-tourism.
One doubts that the restaurant staff are tourists? You seem to be saying that they aren't Icelandic, however.
I don't see this as a wholly bad thing, but the negative impact is that the people you interact with in the service industry, are not able to converse with you easily.
Imagine living in mexico, walking into a mexican restaraunt, and having to order in english because the wait staff and kitchen can't understand spanish.
It's not the worst thing that's ever happened, but I do miss being able to speak my native language outside of close circles.
It all comes down to the question "who do you think you are to block my path?" It's not a straightforward answer, though. We've been struggling to answer this as human beings since forever.
Hugh: Ah, yes well now you see, I have campaigned for years now to have tourists banned from Venice.
Stephen: Have you? Have you?
Hugh: I have, I have. It sounds very harsh, very cruel, very ...
Stephen: Deglante?
Hugh: Very deglante, thank you. But I'm sure it's the only way.
Leslie: Who was it, who was it, who said "He is a tourist, you are a holidaymaker, but I am a traveller?"
Hugh: Oh, was it Humbert Wolfe?
Stephen: It was Cocteau, surely?
... etc., etc...
Where before you had to hire your home travel agent to hire a local guide overseas (and know who), you can now do it all yourself via SM.
That massively improves accessibility.
As it is everywhere. If two people don't pay taxes, society functions just normally. If everybody doesn't pay taxes, there is no funding for even the most basic programs. When the argument is "a bit is fine, just not too much", the second part of the argument should always be "and here's how we determine who gets to enjoy it and who is forbidden from enjoying it".