When to use captions to convey information? Sometime, telling is better than showing. Use with care ... as with any technique.
If you are writing in someone else's narratorial and authorial voice you are likely not writing to your strengths. If I vote in the voice of Douglas Adams, characterisation would take second or third place to ideas. Douglas Adams himself agreed the Arthur Dent was a stereotype. The hitchhikers was about ideas not characters. Wilma and housemates is about both. If I had to choose characters are more important than ideas this is because a character such as Sheldon Cooper can literally last hundreds of episodes and idea can't however perhaps a setting can.