I don't know how big an issue the Yak or Spits have been, they're just planes imo, but I can tell you some simple UI overhauling would have gone a long way to help. Instead of just saying that and leaving it I'll give an full example.
Lets look at the main game screen, when you first open it and talk about flow. Especially new player onloading flow. First off, stop assuming that younger people don't have the brainpower to handle this game. Most of my friends are in their early 20s and can handle DCS level complexity without physical checklists after a few hours. Kids aren't any dumber than they were 20 years ago, but they are MUCH pickier about how much a game can run them around in circles (outside of gameplay, inside of gameplay they're much worse lol) before they give up and try something else.
I would use images, but I'll stay clear of that for now as I'm not sure how well my screenshot softwares links would work here.
So, you have the main menu open and you're a new player, this is the immediate flow.
1) you're hit with loud, fairly short looped music
2) you're hit with the YT videos massive bass boom (that you don't care about)
3) you're given 12 different options on the kneeboard.
I'd like to bring up that my fresh install nearly blew my headset out with 1) and 2), but that's going to be a very personal system.
So, instead lets look at the buttons at our disposal.
-Online Arena
-Offline Missions
-Offline Practice
-Choose Terrain
-Graphic Detail
-Controls
-Training Test
-Account Admin
-Video Settings
-Release Notes
-Log Out
-Quit
We can put these all into a few groups, but something that I think is very important is actually missing from this list. Preferences. You have to go into an offline arena -> Options - Preferences to get to that. Why is that important?
Because you just started blaring a loud, and fairly short looping song at a new player. Their immediate response is going to be to turn it down and the sound options are basically hidden.
Lets go back to those groups though, and assume you move Preferences into the list.
Now we've got
-Gameplay related
-Online Arenas
-Offline Missions
-Offline Practice
-Choose Terrain
-Training Test
-Settings related
-Graphics Detail
-Controls
-Preferences
-Video Settings
-Account related
-Account Admin
-Log out
-Other
-Quit
Now then. There's nothing really neat about that either, there's cross referenced things. But lets say we could lower it to a few less than the 12 options. You start to create a workflow for interacting with this part of the game. Assume the main categories on the next list open into a right hand side category (much like how options -> preferences does on the kneeboard in 'sim'.)
-Online Play ->Online Arenas
->Acount Administration
->Log Out
-Offline Play ->Offline Missions
->Move Training Test into this section
->Offline Practice
->Choose Terrain
-Settings ->Graphics Detail
->Video Settings into this section
->Controls
->Preferences
-Quit
Suddenly a new player is given only FOUR starting points for how to start interacting with the software that branch out to things that logically make sense. That's what you have to keep in mind, they don't mind complexity but they don't want their chains yanked and run around in circles. If your argument is that younger folks don't like complexity then I kindly ask you to go google how much Dwarf Fortress has just recently made with its UI overhaul and to rethink your position.
Now. I would add another left side main tab to this list. This would include all the videos that you've already made, and maybe more. Reaching out to the community to make new ones wouldn't be bad, as people always love getting involved naturally. It should be noted, Gen Z hates randomly playing videos in things just as much as we hated flash videos randomly playing noise in IE on Windows XP 18 years ago. If they want that information they WILL seek it out.
-Training
->Basics - Would handle showing where everythin is in the UI, how to set up your controls, etc etc. It would basically go over all the actual control options and how to capture bases!
->Aviation - Broken down into sections for fighters and bombers, no need to go into massive detail but point people in the right directions. This is a great place to drop info like 'look up Fighter Combat by Shaw' or things of that nature. It of course also needs to be the videos you teach them how to bomb in, use rockets, the whole nine yards.
-> Ground and Sea Forces - Pretty self explanitory, same as the aviation side but for ground units.
->Other - This would handle things like setting up your squadron, using the CV in game, maybe even going into detail on strat raiding and things of that nature.
I'm not going to say that what I've written here is by any means perfect, but it really goes to show what people sort of mean when they say 'the UI is clunky.' Which it is. It's also usable, if you have the willpower to push thru it or someone to point you in the right direction. Assume though that they won't be, and won't have that person there to help. I can say from very recent communication with my group that they 100% would not have pushed thru the UI. They're glad they did, but without an older hand that had used it before being there to inform them it would have been for nothing.