Your question is absolutely right and we get this quite frequently.
1- We or rather ant expert/consultant/investor get 100 inquiries per week, out of that 10 are based on innovation. If we start copying business ideas, then we need to start 30 business in a months and 360 in a year and I think that is not possible.
2- If you don’t disclose ideas with any of the experts then you will not get ahead with idea, by the time some may start offering same things.
3- There are so many things you need to develop like business plan, funding, website, app, marketing material and at this point you need to disclose the idea.
4- People can copy idea but not you. You are the only person who can build it better than anybody else.
5- Find the people, make relationship and create trust and then sign NDA. This is the only way out.
You can catch me personally for more details.