Every group of heroes needs an everyday person who fought alongside them all the way through. Connie Springer is that man in the anime Attack on Titan.
The actions, motivations, courage, and choices of the Attack on Titan girls make them more interesting. They're powerful and always have an impact on the story.
The reason behind Eren Yeager's choice to proceed with the Rumbling is related to a lesson he discovered while watching the Levi Squad in Attack on Titan season 1.