Constructive feedback is well-considered, going beyond a knee-jerk reaction of like/dislike and starts by asking oneself, what could be improved here so that it works better for me?
While all feedback can be helpful, considering the many limitations on each of our resources (particularly time these days), the most helpful and forward-looking type of feedback, to my mind is this type of constructive feedback that considers not just what is wrong here, but what could be better here?
See also: make a proposal