[mixmastamyk]

Static typing is not very important for new, small projects where the developer can keep the whole thing in their head. It can even be a drag during the design phase if the design is changing rapidly due to the added overhead of changing interfaces. Progress has been made reducing the overhead in recent years and proponents may disagree.

Fast forward to when the same project grows and matures. Now it is huge and no one knows every subsystem. The original developers skipped town years ago. There are -1x to 10x developers on the team, and contractors who must "hit the ground running." Static typing is now crucial to prevent the whole thing from collapsing like a house of cards.

I recommend the best of both worlds, such as prototyping in a productive language, then port when the design solidifies. Or, use a language that can be gradually typed later as your startup matures into an established company with customers that rely on it.