The only comparable one I play these days is IL-2. What it has over AH? A single player mode. Not a particularly good one, and I resolved to using an external tool to create a better career mode - but still, there is one.
I also used to play War Thunder a lot (only tanks, not flying), because it was cheap and gave me some quick action, but I stopped about a year ago because of some design decisions.
What can be done to attract those players to AH?
Nothing.
The past has repeatedly shown that the core problem is that people don't like the game. Thousands upon thousands of people have tried AH, and almost none have stayed. The retention rate is abysmal. In my opinion, you would basically need a fundamentally new, modern game to have any chance of keeping them, and I don't know how that could be done.