Shero did a great job until 2012. He was great for building a winning culture and he brought in guys that the core could learn from (i.e. the opposite of Edmonton). He was known for not signing old guys to multi-year deals, making good trades using upcoming D, signing vets who were positive presences and not re-signing guys that didn't deserve it. After 2012 that all flew out the window and as you said, he held on to the nostalgia. I had absolutely no complaints about Shero until Bylsma sank the ship in 2012 and got re-signed for it.
Not trading Orpik, re-signing Kunitz/Dupuis, Bylsma, Adams, Scuderi all happened after 2012. Sure, he probably had that in him the whole time and he was always going to be bad at that point, but until then, apart from giving Bylsma less rope, what would you have wanted different?
He seemed reluctant to take more of a risk with his later picks as well, now that could be more of a franchise upper management issue if anything, but as I recall, the guy had more say in his decisions than JR or the next GM's ever will.
Under Shero, he gave a coach that couldn't adapt his vote of confidence, traded away picks and futures for veterans knowing his coach wasn't going to use them right and when he didn't, he didn't have the balls to correct that situation at all and sealed his fate with his nitwit counter-part.
Shero got lucky, adding UFA's here and here that made the team run but it also taxed the crap out of Malkin and Crosby and they seem/look like they are feeling the full brunt of that now.
And yes, the countless bad extensions for players he should have moved on from or when they were on their final years, he could have gotten something for them, but let them walk for literally nothing.
JR had to fix all of that, he made a bone headed trade (again, partly his fault, partly whomever the hell else is the committee that voted for that as well) with the Despres one, but outside of that, what are the complaints?
He brought in depth with the Neal trade for Hornqvist and Spaling, he traded a 4th liner and a 1st for Perron and added 2 solid pieces to the top 6 with those 2 trades, then went and got Comeau and Downie for 1yr deals, traded the passive Goc (Because him and Sutter were just too much for the bottom 6 in terms of passive play) and got Lapierre and Winnik...he was a guy that seemed to be on a lot of teams' radar, likely less stinging than the Murray trade by Shero.
I mean, I am not a fan of JR's, but I feel like with the restrictions he has and probably not making some of the moves himself, he's done an ok job fixing some of Ray's moves/problems.