If you are a 3-person SaaS startup and your team is spending 15+ minutes a day just scheduling meetings among themselves, and need additional software just to manage that process, I'd say that's a problem in itself.
If that's internal meetings, absolutely, that's an issue. But I think a company that size that's trying to iterate on their offering should be booking a lot of meetings to talk with customers and potential customers, and that could easily take 15 mins a day in my experience.
Someone said this in a comment above, but in a 3-person SaaS, everyone works sales. It's likely they're scheduling a huge number of meetings with external folks.