Part of the problem is a communication one. There are posters who are posting in good faith, making cases for their position while others are simply throwing out drive by suggestions with no apparent objective other than to be on the record in a thread. In short, its a messageboard.Great point.
Two factors are involved imo. 1. Some people are far more focused on a guy's PPG and 3pt than others and largely disregard offensive efficiency and/or defense (especially defense). 2. Some people are focused on beefing up the depth/glue pieces on this year's team with less regard for next year and the year after.
You're right. Nobody is going to argue that dumping Green and adding Porter or Gordon hurts this year's team. That would be stupid. But moves don't happen in a vacuum. Moves potentially preclude other moves later. They also steal developmental minutes. And there are style fit issues and, to a lesser extent, cultural fit. These things all matter.
So I'd say that a good debate on the pros and cons of a guy like Porter or Gordon is in order, rather than "wtf is the matter with you, Porter is great/junk".
That said, if people are advocating a player as an acquisition target, it would be helpful to understand why both quantitatively as well as from a fit perspective. To be clear, fit doesn't just apply to the TPE and a player's contract.