I agree, the term "mission" has become a hackneyed startup cliche. A better way to put it might be, "you think the problem the startup is trying to solve is an

I agree, the term "mission" has become a hackneyed startup cliche. A better way to put it might be, "you think the problem the startup is trying to solve is an interesting one and you are motivated to help solve it". Great startups don't necessarily need an important problem to solve, such that solving it might be described as a mission.