This isn't really a good question for r/askhistorians, since it is a political science question more than anything else.

But the definition of democracy your professor gave is really weird and I don't think is accepted by modern day scholarship. The standard democratic model we have today for instance, are Liberal capitalist democracies under which individual property right and private ownership of capital is guaranteed by law, and elected governments are allowed to some degree to regulate the use of properties of its citizens.

So unless your professor thinks that modern day Canada or Sweden or Germany does not constitute democracies, I don't think his premise is a very good one.

E: forgot a "not" in the second paragrah

As stated in the subreddit rules questions must be about the human past or the study of it. I am afraid your question is about neither of those things, and so it has been removed.