"Supergirl" will get a second season but it will do so in Vancouver. I guess the thought is that the show will appeal to a niche audience who wont mind a smaller CW budget as opposed to the CBS budget. From some of the pictures that I saw last year, I thought that "Supergirl" would have a darker more "Arrow" vibe but the show took a different, sort of, meandering direction.
After watching several episodes of "Supergirl", I wonder if the producers know what to do with the show. The story-line stumbles and lacks a certain continuity. The overall writing is poor at best. I really come away with the feeling that the show's producers don't have a feel for or a direction for the show.
It always comes down to three things; writing, writing, and writing.