@GinDaddy you make an interesting point and very eloquently. But I'd suggest that rather than a non-inclusive classist clique, a better analogy would be that of a club. Say MN is a book club. People join from all walks of life, with all sorts of opinions, and they discuss a huge range of different books (topics). The convention is that they should follow the rules of the club as members, both those rules are set out in a written constitution (the talk guidelines) and those that are unwritten and customary which form the culture and history of the book club. These are a condition of membership. Now, as the membership changes over time, the customary rules and culture will change, which is perhaps what is happening now.
I merely lament the changes because I'm more familiar and comfortable with the existing culture, having been a member for some years, and it forming part of the reason why I enjoy the club so much, because it appeals to my sense of humour, respect for kind honesty, and interest in varied topics.
Change is ultimately inevitable, and maybe I should embrace it in this instance, but it means that the book club is no longer the same one I joined, and it feels less like I belong here. I don't believe that is cliquey in the way you present it, unless the whole of MN is the clique, but there shouldn't be loaded words like mean girls, nastiness etc. I am absolutely not supporting any spite. I just think that new members of any club should aim to fit in and follow the rules of the club.
Perhaps that is unrealistic. But surely those who want to sprinkle sparkle dust on everything should know that MN is not the place for that?