For its days, Space Invader was consider a graphical treat, it certainly requires twitch reflect and is one of the granddaddy of all 'dodge and shoot, shoot and dodge' game (in fact that is the entire gameplay!). The amount of time you spend on space invader depends invariably on how good your reflex is.
How does a game of Space Invaders end? By either finishing the entire game (is that possible?) or you dying. Thats either one damn long sitting or you dying and going away.
How is that different from the campaign mode of any First Person Shooter? You play and either die and give up you get to the next checkpoint / save. If anything the artificial checkpoint most game create nowadays ensure shorter gaming duration because they create artificial breaks.
The only point you have is simplicity, the nature of a game being 'pick up and play' which you consider mature. But again this is a matter of perspective.
FPS, one of the genre you lambasted about is notorious for its 'pick up and play' appeal, it is this very nature that made FPS such a huge success to begin with.
In contrast, you have the games like Civlization which is complex, hard to pickup, 'dull', graphically bland and certainly not a popular mainstream game that all the 'hormonal teenager' are going gaga over. It appeals to a niche audience that like sophisticated micro-management in their games and those audience would certainly be offended if you ever went around telling them CIV is not really a mature game becomes its too complicated and does not have 'pick-up-and-play appeal'.
Space Invader is a very poor example to use to try and pick apart what constitute a mature game because it is one of the key precurser of the immature games that you dislike.
Retro mature.
