I have great respect for anyone over 50 who has picked up video gaming. I've run into maybe one or two in my time...never in person, mind you. Heck, my grandmother refused to learn how to use a computer until the day she died. The way I see it, the older a gamer you are, the more respect I have for you. After all, they're the ones who have picked up a hobby that most people had to grow up with to appreciate, using technology that wasn't even invented yet when they were
middle-aged.
Sometimes people lose interest in video games. Odds are it was never a big thing for them in the first place. There's no shame in not liking a hobby; after all, everyone's tastes are different. What's shameful is portraying those who pursue that hobby as a stereotype, like portraying sports fans as potbellied, lovable fools their wives don't understand who get dyed in woad for their favourite team come football season.
Point is, it's easy to bash something you don't know and stereotype it. Look at Fox News for crying out loud! This has been happening for decades!
If they don't understand why you're still gaming, then they shouldn't look for ways to justify it. If they're attributing their loss of the love of gaming as a sign of maturity then they are dead wrong. They've moved on, true...but they're not more mature for it. Not any less mature either.
Heck, you've gotten laid. You've proven you can live a normal life. Why can't they accept that it's a healthy hobby? It's not like you're a star trek fan or something.
(P.S. Science Fiction nerds are often misrepresented as lifeless, socially immature outcasts. I don't believe this to be true at all.)