Here's my 2 cents being a relatively new join and younger than average (35). The reason I tried it out was 100% the scale and freedom. There are nicer looking and more realistic WWII sims out there, but none I found that had 24/7 persistent dynamic arenas that could hold 100's of pilots and with the full selection of aircraft available from the beginning (other than a handful of perked). That's why I tried it.
How I found AH was a bit of a journey. I was itching for a multiplayer flight sim as I was sick of just fighting AI. Hated the arcade style multiplayer games and the short, single engagement match play. I remembered seeing my Uncle playing Airwarrior years ago so I did some google searching and that led me to AH. My point is I only found AH because I was already aware of and searching for its predecessor.
When I started I liked that there was nothing that put me at a disadvantage being a new player other than my severe lack of skill. No grinding to unlock better airframes, weapons or boosts. I also liked that I could do whatever I wanted. There were no set objectives, if I wanted to try to capture a base I could, if I wanted to defend I could, if I wanted to bomb a factory I could, try to torpedo a CV I could, just furball I could. complete sandbox. The subscription model made me hesitate a lot but considering the scale I decided it was worth it.
I stayed these last 4 years for several reasons. My squad (who I originally reached out to so I could try FSO), FSO, scenarios, and just being able to jump on at any time and try to get a little better at an aspect of the game. I was several months into the game before I knew about FSO and scenarios. I didn't know about this forum and had only heard the odd mention in game. To be honest if I hadn't found the forum and my squad I probably wouldn't have stuck around much longer. Perhaps a link to the forum in the starting menu would help with that?
I had a lot of things going for me that helped keep me here. I was already into flight sims so I had some of the basic gear (joystick) and knew how to fly. I can be really stubborn, I will keep reupping and throwing myself into a fight to try to figure out why I keep bursting into flames so fast, and with the hope I'll learn enough to survive just a little longer this time. High end ultra realistic graphics have never been a deciding feature for me. All of these are road blocks for most younger gamers. Most casual gamers I know bounce from game to game so they look for ones that are easy to pick up the basics, don't require any special equipment (yes AH can be played with a mouse and keyboard but not easily/intuitively IMO), and have lots of eye candy. They described AH graphics as 'ok, not AAA'.
In my opinion tweaking gameplay will only affect how many veteran players leave or come back. Most new players don't get far enough into the game to even notice these things. My suggestion to attract and keep new players would be advertising through twitch streams, more youtube videos, a discord server, maybe hiring a streamer with a big following already to do a feature, stuff like that. And not just advertise the game itself, but FSO and the other special events. Then a series of tutorial missions that go through takeoff, gunnery, dropping bombs, etc. that are easily accessible, but not mandatory, will help them learn the basics. Even "help" prompts in game that can be turned off would work (press '+' to throttle up, Remember to raise your gear with 'G', fire your guns with 'spacebar'). A bit of hand holding off the beginning would go a long way for the average gamer.
I think that would help bring in some ppl but the biggest problem these days is that flight sims in general are a niche market and WWII combat a niche within a niche. There just aren't a ton of ppl interested in this kind of game anymore, and the ones that might be either hit one of the roadblocks mentioned or don't even know AH exists.