I think the Nets got significantly better, but I don't think it's enough to move them up in the Eastern Conference pecking order. I don't seem them surpassing Miami, Chicago with a healthy Rose, or Indiana with a healthy Granger.
As for Kidd, his age isn't an issue; it's that he isn't far enough removed from the league as a player for guys like KG and Pierce to see him as anything other than a peer. The difference between Kidd and Spoelstra is that Spo never played in the league and was a Riley assistant for more than a decade before getting the head coaching job.
With that said, I'm not sure any vet in the league commanded more respect from his peers than Jason Kidd did. Spo was able to handle Miami's Big 3 in large part because Wade validated him when asked by LeBron and Bosh; likewise, if KG sets an example by falling in line, I don't think Kidd's authority will be an issue.