Hi Crashtest
In answer to your question the hobby is a very social hub in my experience. In the two years I have been into Airsoft the community & circle of people I have met (and now regularly contact) has literally changed my life.
I now speak to more people who I have met through Airsoft than the mates I have had most of my adult life. I often get whatsapp messages by drunken fellow airsofters on the Friday night before the next days skirmish just to say hi & ask me what I'm up to. As a matter of fact the community is one of my favourite parts of the hobby.
Fitness wise its not up there with my other hobby (mountain biking) but then again what is? If you are looking for a load of grown ups that are old enough to know better dicking about with toys guns & having a laugh, look no further. If you are looking for a serious sport where winning is everything you've taken a wrong turn at Tesco's.
I'm similar to you mate, I do have a good level of fitness, I used to box in my youth but nowadays hate violence of any kind. Airsoft isn't like I thought it was going to be at all. My image was of loads of ex military guys who were still in the mindset and the sport being highly competitive, what I met was a load of guys having a day away from their wives while playing silly buggers in the woods, I've never looked back mate.
If you don't take yourself too seriously then come aboard mate, welcome to a future doing tactical clearances of your bedrooms in your socks, pretending your new gun is the one you have had for ages & eyeing up kit you don't have any use for but you still want it anyway. Leave you bank card at the door because its going to get abused for a while