My general thoughts on the subject, not pertaining to CG :
Roleplay is a cooperative aspect; it is at its heart, a play upon a stage and we are its actors. In roleplaying with an individual, they are given an equal share of your story as much as you are given theirs. Fundamentally speaking, if you do not wish to roleplay with someone they are not involved in your story.
Newer persons to the 'established community' have little reputation to gauge for what they bring to the table. If they present themselves in ways the community operates, they are easier to evaluate and take in. If they behave in ways different from community expectations, it is more difficult to determine their worth. Thus, in certain respects, persistence is important as much as social awareness.
The backbone of any good community is the relationship they have at the out of character level. Not in the sense everyone is friends or Friday night drinks buddies, but people are known values. If a random alt of a person I considered excellent showed up, I would be likely to engage them. I have reasonable expectations that what will follow is to my standard, and life will be good. Contrast with a character of unknown origin; I most likely will not seek to be involved with them beyond a cold shoulder. My time might be wasted if they prove to be of undesirable values. Thus, I have to consider if my time spent on that risk can be worthwhile or not.
Others are considerably more open, mind you, but you can understand from the view point of someone who is insular.
In this respect, then, the community can be 'hard to get into', but only in so far as every other community. If you wish to participate in the community, you need to establish yourself with reputation that you want and is also attractive. If you are one who disregards norms, you will attract those who also disregard norms and repel those who follow norms. If you are one who prefers partners over community, you will attract partners and not free-floaters. So on, so forth. Like attract like is a very powerful social mechanism.