I think with D&D, grog has a more specific meaning because we've got a bit of a generation gap, and whilst I think it goes later than that, it's unlikely many people born in the 1990s or later qualify as grogs.
And as
@Umbran says the groaning is a key part of it. If you don't complain about modern games or newfangled things, you might be old enough to qualify as being a grog, but you aren't really one. I've yet to see a TT gamer under about 35 do the "back in my day!" groaning dance. I have seen people under that age advocate for some pretty old-school games and go on about how cool they are, but that's like kids rediscovering Phil Collins and stuff, they're not groaning that modern games are bad - especially as a lot of the best OSR games are, well, really modern!
And will there be, like, 5E grogs one day? Probably. But I think it'll be quite a while. I don't really see any 3E or 4E grogs, for example.