I feel like Citadel gets a bad rap for being the default option when playing instant action, I believe this to be untrue as it's unbalanced nature is actually what makes it good as just like upward in TF2 the joy comes from the natural asymmetry in the map alongside symetrical mechanics.

But onto the main point, the fact that only two points are valid spawns when playing as blue (eagles)(the default option) means that alot of AI buddies are there with you from the start and the enemies are more spread out and alot of them will being wasting time fighting helis or walking to the bunker allowing for a good initial push and then the mountain pass is basically impossible without teamwork or Remembering that smoke exists even in vannila, then in the courtyard (imo the second hardest point on the map to cap as it is in the open and the enemy has both cover and good sight lines) you either have to flank or work alongside your team lest you lose troops quickly, then finally the last point that the player will probably cap (i forget what its called but its by village and is the north-most point) is all in ravens favor so the eagle team will have to use both teamwork and special-weapons carefully if they wish to succseed.

However just because its a good map for beginners by teaching them the importance of a lot of mechanics is also what makes it a bad map as it has a TON of very hard choke-points that stall the game until a tank respawns or you get lucky on AI weapon loadouts

So TL;DR map is good if your learning but bad if you arent willing to sink some time