Apparently you aren't very familiar with the Xbox demographics. The largest age group is in the 25-34 year old bracket, followed by the 35-44 year old group. And more than 50% have an annual income over $50,000.
https://www.windowscentral.com/heres-some-interesting-stats-about-xbox-one-owners-microsoft-shared-partners
Browsing through game forums, there is interest in a more realistic sim, however, many get turned off by the complexity of the current sims themselves as well as the outdated graphics. And by complexity, I'm not talking about flying an aircraft, but the actual sims themselves (too much messing with config files, install locations, issues installing add-ons etc.). Not to mention how poorly they can run on modern hardware (and yes, plenty of people under 30 have PCs just as powerful as anyone on this site does).
When it comes to attention spans, many people in the gaming world have no trouble putting plenty of time into them. Open world and RPGs are quite popular and often allow users to come up with their own objectives in the games. Check out Eve Online and the complexity of the universe that has been created for one example.
Here are some examples of things users have put together in Minecraft. Not exactly something that a person with a 5 minute attention span would do.
http://www.escapistmagazine.com/news/view/109385-Computer-Built-in-Minecraft-Has-RAM-Performs-Division#&gid=gallery_206&pid=1
http://www.industrytap.com/minecraft-player-creates-game-calculator/22760
Of course Microsoft is choosing their words carefully, one always does when marketing software. Give too much info up front and you get in trouble later for breaking "promises" when something changes.
They don't need to make a sim that attracts everyone in the gaming community, just one that gets the attention of those interested in flying, which is something that spans generations. Plenty of younger people are still interested in flying and becoming pilots. A good sim can only encourage that.