A clear concern raised early can protect a plan people are still excited about.

Concerns get harder to raise as enthusiasm grows. Early on a doubt is useful, and later it sounds like disloyalty, so people hold their reservations until the problem is undeniable and expensive. The plan then fails for a reason somebody knew in the first week. Speaking early is what protects the thing rather than what threatens it.

Say your reservation while the plan is still being shaped, framed as a question about one specific risk. Make it easier for others by thanking whoever goes first.