This just got ignored by everyone... Quite unfortunate.
You are right, it is - in my opinion - probably the best analysis of why we don´t even get people into the game to TRY it - let alone stick long enough to see it´s potential.
The GUI is a big thing. X-Plane did not see success with a larger number of players until they revamped the GUI with X-Plane 11. The core simulator didn´t change that much, but just having a modern, industry standard and decent looking GUI made a huge change!
Aces High´s initial experience is so 90´s. That was a time when players went through a lot of trouble to get to play a game. Not anymore. Modern players are used to a smooth and hassle-free experience, with big, glowing, pulsating buttons showing them what to hit next to continue. Every successful online game has a foolproof interactive tutorial and tries to make a perfect first impression.
Yes, the Aces High GUI can do everything it needs to do - but we are blind to how it looks to a modern player because we have stared at it for 20+ years.
This is not the only reason that Aces High is slowly dwindling into extinction. So the real question is: How much effort does HT want to pour into different lacking aspects of the game to make it viable?
The problem is not lack of advertising. It is not lack of aircraft models to fly. It is not lack of interest in flight simulation (see War Thunder?). It is not players not liking complex games. It is simply an outdated visual experience (both GUI and in-game) and a horrible gameplay experience as a new player (long, dull flights to get to the action, impossibly hard adversaries).
The changes necessary would be expensive and probably also not sit well with us old **rts that just like the game the way it was when we started playing it in the 90s as young whippersnappers.
Jan