I feel that Barrie's concern was not as simple as "not wanting to grow up". What I get the sense of, when I read his plays, is a distinct tension between a constricting and solid reality, and a fanciful escapism to a world of ignorance to all reality. It is not so much maturity as the mundane, and the social pressures of contemporary life, which is so unfavourable. Peter Pan represents an aversion to change, an avoidance of pressures to conform to hideously monotonous standards, and an escape from judgement. I feel as though JMB is a man who sees so little to truly connect with and be thrilled by in reality, that creating the idea of a blissful ignorance (to resort to cliche, I apologise) in which flight, freedom, the whole lot are available and one would not be frowned at for embracing them.