How a builder communicates before you sign is the most accurate preview you will ever get of how they will communicate during twelve months of construction. The vetting phase is the only time that information is free.
Your builder isn't returning your calls. You're not being dramatic. You're being ignored. And the instinct most buyers follow when this happens gives them almost no real protection.
There is one question that changes everything: Can you give me the names of your three most recent completed projects? Not your best. Not clients who are comfortable talking. The three most recent, in order.