Is it justified for a teacher to refuse your project proposals just because he wants something unique?
It sounds like the standards are pretty high. It sounds like the instructor doesn't want you to be mediocre. It sounds like they are demanding some creativity.
Those are good things, actually.
It is hard to judge whether the standards are unreasonable or not but you would benefit by meeting them.
Are you permitted to brainstorm with other students? Do that if allowed. Have you asked for ideas from the instructor? Have you tried to take any of your original ideas and modified them to come closer to the standard? Alternatively, have you taken any really hard problems and tried to whittle them down to something that is doable and meets the standard?
It's good that you aren't being singled out, also. The farther you go, the higher the standards you will be expected to meet.