I read B'elana as a point that the chief engineer doesn't always need to be some composed nerd. Even a person with deep anger control issues, with interest in (Klingon) religion, can be a good fit for that position and can stand her ground to a literal Borg.

Plus ofc Janeway + B'elana and + 7 later, meant that most science-related decision were made by a group of women.

But as everyone on the cast, once 7 and doctor were out, the screentime was really compressed 😶