If that's how you feel, then fair enough YANBU.
That said, you moved out of London for a reason presumably? Do those reasons still stand? If so, and moving back is genuinely unachievable, I think it's possibly best to focus on the good things about where you live- or perhaps look into moving somewhere else which suits you better.
However, I do find the suggestion from a number of posters most people in the "provinces" (or anywhere outside London?) are narrow minded/ have never travelled/lived elsewhere more than a little patronising. Yes, of course the smaller places are not as culturally or ethnically diverse as London but there's a difference between that and narrow-minded.
I live rurally, and within 30 miles of where I grew up. I have lived in several large cities (including London) in both the UK and abroad. I know many people who have a broad range of experiences and some who have always lived nearby. Not had any problem integrating into the community and don't find it "narrow-minded". Obviously, activities and amenities are nowhere close to the breadth and depth you'd find in London but not all poorly educated, backward yokels either.
Moving to a new area is difficult, and making friends takes time and effort. It can be a lonely time. However, I have often found those who say they are treated as "outsiders" are the people who don't make a huge amount of effort to get involved in the local community either.
I know of one person who felt ostracised for being an outsider was actually incredibly patronising/condescending about the locals and the area (which she had chosen to move to!) and was very keen to inform us about the lack of "cultural opportunities" and how where she had moved from was much superior. I'm not saying that is you, OP, but maybe worth considering how much effort you have made to integrate into the community?