1. Demarcus Robinson was one-and-done for Baltimore Ravens
The Baltimore Ravens legitimately needed Demarcus Robinson, and he ended up being the best wide receiver on the team by the time the playoffs rolled around. However, that may have said more about the Ravens' receiver room than it did Robinson, and the team knew they had to upgrade.
First, they added Nelson Agholor. Agholor is at least a close comparison, but you could make the case that even by signing Agholor they upgraded from Demarcus Robinson. Of course, that does not even mention Odell Beckham or Zay Flowers. When you add in that Rashod Bateman is currently healthy, the room went from empty to crowded relatively quickly.
If the Ravens signed Robinson now, he would be competing with Agholor for that fourth spot. That is why Robinson is not even interested in returning at this point.
In this case, it was actually a good outcome between the Ravens and Robinson. It was just a one-year thing, but the Baltimore Ravens needed Robinson, and Robinson needed the Ravens, Now, neither side needs each other, and they will move on.