I think "cautionary tale" is a bit hyperbolic. It seems to me that the author's motivations for getting into photography and expectations of what it would bring to his life have as much if not more to do with his experience than Instagram.
If you get into photography for the purpose of garnering attention and praise from others, rather than, say, telling stories you find important/interesting or chronicling your experiences visually, your odds of being disappointed are incredibly high. Everyone is a photographer these days thanks the camera we all carry in our pockets and as a result the supply of photos far exceeds the demand.
Note that this is not to say that Instagram hasn't had a negative impact on photography. As an avid traveler, I think it's both sad and amusing that people take basically the same photos of high-profile tourist sites to post on Instagram. But of course that shouldn't discourage anyone from taking photos when they travel if they really enjoy doing it, which is probably the only good reason for the average person to take photos anyway.