RCMS hang in there, buddy. As a former military brat who attended 10 K-12 schools in 12 years and 4 colleges/universities (lots of grad school) across three states, figuring out where I fit in was always a challenge. I've lived in urban, suburban, and semi-rural environments across several states, and one of the many roles I've served as an adult were running club newsletter editor and director for a fairly large community in Northern California.
My 3-cents of advice:
1. First, understand there are good people everywhere. When you start letting people in and getting to know them (difficult I realize for an introvert; my wife is a pretty strong introvert), you will be surprised how much you may resonate with someone on various levels, no matter their background or how they look. This may take several weeks or a few months, but you may develop lifelong friendships (however deep) in the end. From my experience, runners tend to more introverted than other groups of people (like your typical corporate environment); it could be that the running group you fill is stuffed with unrelatable, even snobby types actually has a lot of quality individuals who just want to be known as much as you, but don't really know how to go about it
2. Every club of any kind that has lasted for a few years likely has a cliquey core. That's okay. These are often the lifeblood of the group; the folks who make volunteer their time and make things happen for their members and the greater community. Without folks like them, our towns and cities would be poorer places. Focus more on appreciating what they provide, instead of what they lack. Then, look elsewhere for what else you need socially.
3. Look for a group that seems the best of the lot in your area, as far as interests and personalities go. Spend some time earning their trust by showing up regularly, and pitching in if and when you can. Then, if still interested, offer to join or be a part of a club initiative that could allow you to reach out to a broader swath of the community. Be the change you want to see in the club, but in a way that builds club bridges instead of weakening or destroying them.
4. Otherwise, consider getting what you need from an acceptable club for your training and racing support needs, but fulfill your need for deeper companionship but trying out new social arenas: Meetups, supplemental workout places like gyms, community events, college activities open to the public, etc. Develop levels of friendships; 1-3 or so for the really important stuff like support for the big moments in life, etc.; another few for shared, substantive interests like deep conversation; then others for just stuff you like to do, without a care/need for anything beyond that.