In my opinion, it's easier to play as Conflux than as Fortress. It has fast wyverns and a ranged unit stack.

Well, my post was aimed at complete beginners, explaining that it's easier to play as Conflux because they often leave their castle (as beginners) only in the second week. And magic users make life easier with this playstyle.
I don't know, when I was playing poorly, I always suffered losses with melee units, but with ranged units, I slowed down and killed enemies, and finished them off with magic where needed. Therefore, the efficiency with mages and ranged unit stacks was always higher. But this is due to my inability to play with melee units, not because they are weaker. I think all beginners experience the same problems that I did, which is why they consider Citadel and Fortress to be weak.