@khabume, I cannot see the majority of people leaving because of Gap, just a select few who have enough experience of the game to know otherwise. For it to be as high as 40% seems way too high as this would account for numbers in the hundreds leaving per month which would be very obvious in the multiplayer community. If that claim is right then about 600 players are leaving FAF a month due to this reason alone. If you want you can see the stats in the forum posts linked. Babysitting new players also isn't an option, if people want help, they are old enough to ask for it.
My original point was that I think the majority of players who leave FAF are those who go completely under the radar I'm talking people about who get the game, play it for a week and then leave. Their reasons for playing are mainly based around being able to play an old game again, with the possibility of cool mods, coop campaign and possibly the attraction of multiplayer. Now those first two reasons, the mods and campaign require little community interaction and you'd expect these people to disappear in a matter of months, let alone 2 years. Now rather than looking at reasons why people might leave isn't the view we should be taking, you could be playing 100's of other games, why stick to FAF. Community will be an integral part for those who do play for over 2 years. Its nice to read comments saying that people can get on with the community.
Maybe what's required to increase retention is to involve newer players; have regular events each week such as group teaching sessions (different to babysitting players as the emphasis is finding people with similar skills to encourage early friendships/rivalries). Noob friendly nights where someone hosts different maps throughout the night specifically for new players (as @Amygdala suggested earlier)are also a good idea, again with emphasis on creating common friendships and rivalries. I feel this would be far more effective than any rebalances/babysitting as people will learn if they have an incentive to learn, they won't learn if they are being spoon fed missions vs ai. The idea is to routinely allow newer players a couple of nights a week where they can interact with one another and build this community. I'm happy to even regularly host one of these idea's a week. If @nine2 is onboard, you can feel free to PM and I'll work with you on implementing some of these newbie events.
Saying that, no one has mentioned the elephant in the room here, 90% or so of new people are leaving FAF is because some major worldwide pandemic might have resulted in a large influx of players who simply don't have the time to invest into the game under normal circumstances, and so these people are more than likely to have joined, played for a bit during lockdowns, and then left. Even many of the older players who had left came back to try again and have since left again. FAF is still growing, people will come and people will go. You cannot force players to stay, and many won't see FAF or Supcom as a long term game. As long as the influx of players is greater than those leaving then is there an issue? I can't see there being one. This will hopefully be the last long post from me in a while.