Yeah, I find that attitude quite counterproductive in software development. I understand and agree with the argument that some “can’t you just”s are way more complicated than they are presented. But this kind of attitude, taken to its extreme (e.g., having that sort of half-joking sign on your door) is a roadblock to real progress, which often starts with a “hey, couldn’t we...”.
For me the point is that inserting the word “just” is diminishing or belittling the person's contribution, even as you are asking them to make that contribution.