The problem is your boss does not think you are a good employee. He would rather do your job for you, even if that means ignoring your analysis in favor of what he has surmised you were trying to tell him.
Please deal with that problem. You can try writing a detailed question for us where you talk about what went wrong in your relationship with your boss that has led to this situation. Or you can do lots of reading on your own on what is a rich and complicated topic.
Sure, you can leave, but as it stands you'll be a second-in-command who leaves whenever you can't properly manage your own relationship with your boss. That's quite a critical skill to be missing. (Or maybe you really are talented and your boss really is not. In which case, sure, you can leave.)
Just some ideas, of things you can say or ask your boss:
- "I was wondering if you could tell me what you think made him a stellar employee?"
- "Do you admire his position? Is there anything about it you feel you can't do?"
- "I'm worried that we've been making mistakes on issues that I had the right insight on." (riskier! but more on the right topic!)
- "I view employee recommendations as a really critical part of my job and think I'm good at it. Are there other skills that you value in me if you don't want my opinions on these matters?"
You also have the option of strategically jeopardizing your relationship with your boss over this. "This is a big deal. We will fail if we mess this up. I will not work on a failing startup."
But like I said y'all got problems. So good luck.