I don't think it was that The Cage was necessarily light on action adventure; it was that there was no action/adventure sequence at the end of the episode as part of its resolution. The Action was mostly in the middle of the episode and the ending of the episode was a long intellectual like soliloquy.
Networks wanted the action properly spaced out and they always felt that an action sequence at the end of the episode was best, and it was better if the entire episode led up to that action sequence as the story resolution (which is probably why in the second pilot you have the big physical confrontation between Kirk and Gary Mitchell as GR realized how the network suits wanted the story action structured to keep an audience's attention/interest for the full 55 minutes and not turn that dial before the end.)
I mean if you really look at it Where No Man Has Gone Before is mostly a lot of talking up until the end fight between Kirk and Gary Mitchell; but with the action at the end, that's the last thing the network suits saw and remembered about the episode.