I am sorry, but what is wrong with your professor? You were doing exactly what you are supposed to do in a peer review. You should go look for things that are wrong or should be improved and only if the paper can withstand that process, it should be published. Only providing positive comments is really harmful to the scientific process and, in the end, to society.

To be honest, I think I reject more than half of the papers that I review. The rest require major or minor revision. It is not that I have a target or anything for how many I need to reject, it is just that most papers are of such low quality that I cannot do anything else. I think the number of papers I reject is quite normal in my field.

So, not all your comments need to be positive. If there is reason to be positive, you should mention it. And your comments should be constructive and respectful, but definitely not always positive.

In the case you are describing where the authors seem to only have read the titles of the papers, I would definitely reject. This is fraud. You are saying you did a literature study and you did not. So, I would be quite clear about that. I would also be a bit angry that they wasted my time. So, in my opinion, that is how a reviewer should respond in this situation, not with only positive comments.