Generally speaking, this may be the least common of the “bad feedback” issues that I see, but it can be crushingly bad feedback. Many, many professors try to force their students to look at the practical dimensions of the project and try to get the students to do less. Almost every professor I ever worked with told me some variation of “do less,” and many students with whom I’ve worked have also been told to try to do less, so I know it’s no rare idea, but some students could really benefit from this advice.
I have two main suggestions here: 1. Get the students to reduce the scope of their project if possible and reasonable, and 2. Explicitly focus on the practical dimensions as a reason to make the project smaller in order to reduce the emotional impact of being told to do less.