It is definitely an interesting subject, I have spoken about this with my sister. My mother, still a JW (since 1960), has never really matured, she is just like a child. She didn't need to deal with "the real world", which meant that her personality did not develop with experience. Just like a child, she was shielded from dealing with adult situations.
Me? Not so bad, however, I will say that I am lacking experience that my husband has, as he was a construction contractor, and had to deal with "worldly" situations and people all the time. He discussed these things with me, but it is quite different when you are "the one" that has to go head to head with someone.
Socially, in JW world I got along just fine, had many friends.... but, of course, they have to be your friend because we are a "spiritual family." I hate to think of what it would have been like if they didn't "have" to like me, as some said, "it took me two years to really get to know you, and I really love you now, but before, I just couldn't understand you... However, after leaving JWville, I did make friends with the nurses while working at a hospital. No problem there...
After you leave......... what do you talk about? That has been hard for me. I don't know "politics", haven't "traveled", am not into "sports"... can't talk about the "games" as JWs are not suppose to be into that. Etc, etc..... That does make it hard. No experiences, no talk....
My sister has been isolated for a lot of her life.... She never got baptized, but was always an "outsider" JW... Being nice to the older ones in the congregation, going to meetings most of the time, but always fearing Armageddon. She was isolated from "the world" and also JWs, as she was never "in" all the way... right? You know how it is, never in the world, never in "the truth.' Limbo... So, I would say that she has been limited also.
Conclusion: Yes, I would say that many JWs are not as "grown up" as they would have been, if they had really experienced "life".