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.