How old is too old for gaming

what is a reasonable age which playing video games is no longer acceptable?

I would say never. Even if you're 90 and you enjoy playing it's still great.

I think as long as you're having fun. There's no too old for that.

there is no boundaries when it comes to gaming

I don't think it's directly a matter of age, for me at least. It's more a matter of time. As you age, you spend more time working, or housekeeping, or doing groceries or whatever. That means less time for leisure activities, so less time for gaming, sadly.