Whether to have everybody sign an NDA/ before discussing your idea is an age old question for new entrepreneurs.
The consensus is that for software startups, concentrating on secrecy is a waste of time for most projects.
It gets in the way of finding talent, funding, market research – all crucial to delivery.
In essence, when you cut off feedback, you're asking for miracle odds that you got the idea 100% right, on your own, without discussing it with anyone else, and correcting for what the market wants. In other words, it probably is perfect for the market – but you've only got a market of 1 (yourself).
Some notes to give background to the above: