Other than that FAF is very difficult to learn and tutoring will definitely help.
I would say that new players run into the below issues.
1- Specific map dominant strategies/dominant groups of players.
regular players in FAF usually stick to specific maps and continue to play them over and over again versus the same players which means that this group of players will be aware of tactics that help dominate the game and crush the opponent instantly. But this is not the issue.
The issue lies in the fact that these players will be extremely underrated in these maps. a player who plays Gap of Rohan over and over again and is rated 800 would definitely crush an unfamiliar with the map player who is 1100. Imagine what is the situation for a new player, he/she would continue to get crushed by players equal to them or lower which will drain their energy and drive them away.
2-Broken rating system:
I don't think that FAF rating system reflects players' true level. I remember some players who were 1600 and then the next week suddenly they are 1100. which means the game gets balanced accordingly and they usually crush their opponent quickly.
3- FAF balancing units towards favoring pros' play style.
AIR is OP, rushing com upgrades is OP. early raids is OP.
I used to play supcom the original version and after moving to faf, I noticed that the way things are balanced is forcing you to play with a certain style.
4- Smurfing Culture. XD
I play FAF like four times a month and I don't know any group to play with and I must say that when you log in to random games you keep getting baited into games with smurfs. although this is not a big issue.
5- Lack of low-ranking players to play with. if you are below 1000, good luck finding a game. with people who are similar to your level.
all of the above leads to frustrating the new players and driving them away and I personally would have left FAF if not for some pros who helped me.
I think solving these issues would be quite the challenge. so good luck.
Also, I would like to share some suggestions that might help per issue. please take them with a grain of salt as I have a limited point of view since I don't play that often.
1 & 2-tweak the rating system.
3- make rushing things harder.
4- the gray ranking system is enough for this issue to be solved.
5- engaging new players and telling them how to find similar ranking opponents & teammates.