Thats a good example but that's within the Federal government.
How would you suggest AOC do that would make a significant impact beyond changing federal law or doing things with funding?
You're missing the point. You're also making a lot of assumptions.
Congress doesn't control the Air Force, the Pentagon, nor any other executive agency. While they have the duty to fund them, they are not sticking their nose into the military's internal workings like ROTC recruiting and scholarships.
You might as well have asked why my mother didn't write a letter to the President as he is the Commander in Chief of the military. In our government, we have Representatives. Those are the people from whom you you seek assistance when you find it necessary.
The influence a Representative can bring to bear on a problem sent to them by a constituent is the point. What someone can do to solve a specific problem is not a defined process. For the issues in her own district, maybe getting the DOJ involved can help. Maybe the problem is a police department that's so corrupt, they don't want to fix the problems because they are profiting from them. Maybe they are doing all they can but need more resources? Maybe they have an organized crime problem which the feds can absolutely address if it spans more than one state.
She can start by at least gathering the answers to some of these questions and others and THEN AFTER SHE'S SPENT TIME ON THE ISSUES can come up with what she can do.
I'm not suggesting she do anything other than take time to address the problems in her district. If she's got the same "not my place to fix it" mentality as you do, then it explains why the people raising the issues are saying she's MIA and nobody there can contact her.
Why do you assume the only way AOC can make an impact is within the scope of lawmaking and budgeting? I sat next to a US Representative for Hawaii on a trip to the Big Island once. When asked what issues she normally spent the most time on, it wasn't federal issues. It was local issues. The federal issues are pretty much orchestrated by the DNC. They send out monthly newsletters that show schedules of speeches and photo ops so they can attend to show participation, what issues are being voted on in chambers, and the talking points for why they are voting for or against the measures. When she was on break from Congress, she went home and held meetings and office hours to discuss local problems and solutions.
If you still don't get it, ask a more reasonable question than trying to put the solution back on me. I haven't studied the problems in her district, so I can only give general problem solving ideas.
If you are just trying to say what you believe, which is AOC can do nothing for her constituents, including picking up the phone when her voters call, you don't need to reiterate that opinion. You seem to know what you know, and posting back and forth is just another one of your thought experiments.