From a previous post where questions were asked of AJ for the reasons behind having one type of map - I believe this provides some insight into the reasoning behind this choice - albeit opinions from players external to AN:
Q: Would you like to see any other map types made for spvp? Maybe CTF for example.
Hey, Guy_With_A_Question. Thanks for the question, guy!
Honestly, no. While it would be fun to have different game modes, imagine the balancing nightmares that would ensue. If this game seriously wants to take itself as an eSport and take a stab at success, I think they are taking the right direction on balancing the game for one game type.
On top of that; this game has amazing positional based PvP. What better game mode to go along with that than conquest with cool secondary objectives for each map?
A2 (TLrotten,Rotten/Team Legacy):
Right now, Conquest is the best mode for the game.
As there are no dedicated roles (e.g. healers), the usual deathmatch and other common gamemodes don’t fit in. The game would have no depth other than smashing all your damage skills.
I believe the reason they chose conquest over other modes is simple: It forces you to split into several scrimmages, creating 1v1,2v2, etc. situations where you have to use your abilities really carefully (like fearing someone of a capture point to cap it, snare someone on the way to a point, etc.)
There are some modes that could fit into the game, as you mentioned, CTF is one of them. The issue would be that the game is balanced around conquest. I think they are definitely doing the right choice in sticking to one map type.
I also need to add that the secondary objectives offer more possibilities to Conquest than other modes. I could imagine CTF being integrated in an actual conquest map for example.