Wanting a player and disliking a bad deal to get the player are two different things. It's okay for fans to really want a player like Diaz, and then turn around and criticize a deal that was made for him.
FTR, I don't think the Mets were fleeced, that is with my understanding that the Mariners are sending $60 mil to the Mets. But if the Mets are taking on most of Cano's salary, then IMO, it's a bad deal for them. If the Mets win the World Series, it will be worth it.