I really do not think that Phoenix is the reason they can't bring talent to the team. I think the problem is the team has a reputation of doing horrible even though they dont look bad on paper.
I dont see how you can compare the Suns to the Cards.
It seemed obvious to me that the comparison was only that the destination must not have been the dominant factor, for the cards, and for the suns. Most players will listen to their agents, if the agent says sarver is a jerk, he goes somewhere else. Suns fans should realize that after the JJ fiasco that agents manipulate players. Many players wont react well to the negotiating tactics that owners will use with agents and visa versa, and the agent can just say, he's being difficult and not giving you what you deserve, "it doesnt look like a good deal". So if sarver is "on the outs" with agents or perhaps is too difficult with them, that FA may go elsewhere and it likely has nothing to do with what phoenix has to offer.
Old guys like PJ Brown and Cassel probably didnt want to run the ball.
Tyron Lue thought he wouldnt get the PT, or perhaps he's another greg anthony or avery johnson(both think they were better PG's than nash).
Finley, probably picked the spurs as a better organization, hard to debate that one.
The ownerships of boston, LA, SA, Detroit, Portland, Dallas, Houston, are pretty stiff competition for a real estate businessman who is relatively new to the business of basketball. Ditching the colangelos too quickly may have had a cost, perhaps the present ownership didnt learn the basketball business savy, smarts, before dumping them.