This attitude kills me every time I run across it. The ones that get to me most are the ones who have been eating Indian Restaurant food for decades and think that is the be-all and end-all of Indian food. While it can be very good in it's own right, what it ACTUALLY is is an Americanized version of the British version of mostly Pakistani/Punjabi food.
So when someone tells me that my Andhra MILs version of some dish or other is inauthentic, I have to laugh. The woman was born, lived, and died in India and never so much as laid eyes on a Westerner in person until her son married one, LOL! Then they'll tell you that actual Indians don't REALLY know how to cook Indian food! But they, having never set foot in India (or perhaps having been there once 30 years ago), know more about Indian cuisine than the people who cook and eat it every day.
Of course there isn't One True Paella. That's like saying there is One True Soup. There isn't One True version of any dish. Human beings are changing things around all the time, that's one of our few charms. If we didn't, we'd all still be eating seeds and grubs, LOL!