VCs get away with it because:
1) They have reputations;
2) They have the money
3) It's a practical necessity for someone who looks at a dozen pieces of IP daily.
None of those cases apply to you, and as a general rule, no competent entrepreneur will pay a contractor who won't sign an NDA.
My recommendation would be to sign enthusiastically, because it means you got a job.
1.) This isn't about getting a job, it's about helping entrepreneurs start companies.
2.) I already had two queries that rubbed me the wrong way because they are similar to project I have in the works. Signing an NDA would probably jeopardize the work I've already done.
None of those cases apply to you, and as a general rule, no competent entrepreneur will pay a contractor who won't sign an NDA.
My recommendation would be to sign enthusiastically, because it means you got a job.