That's not really accurate. I don't think Sam ever spoke about his situation at all to anyone but Dean and Bobby (and he didn't voluntarily confide in Bobby; Bobby probed, once, Sam deflected); it was Dean who talked about himself and his stuff to ghost!Jo, Osiris bartender, Vegas stripper, Frank, Krissy, etc. And some of those conversations did have genuine Dean insight going on.
Which isn't a Dean gets all the development criticism -- it's that they were doing the insight for Sam through his interactions with Hallucifer. I really think it could have worked, and was working up to a point, as an illustration of a different kind of relationship problem. It wasn't that they were at odds. In fact, the Amy thing generated more communication between them in some ways than we saw elsewhere. It's that Dean didn't trust Sam's sanity and wellbeing (not didn't trust Sam) enough to talk to him directly, as with the Amy thing, so his breakdown of coping (and some of his more positive moments -- his interactions with Krissy represented some healing on his part, I think) was spilling on random people while he turned away Sam's attempts to get him to talk. Sam, meanwhile, was locked in his head and scared of what was going on in his head, didn't want to burden Dean when he could see Dean was teetering, and needed for his own defense the belief that he could cope keeping Lucifer at bay, so he wasn't opening up to anyone at all about what was going on with him or how he felt about it.
That situation itself was a problem in their relationship, and it could have worked if there had been a structure of crisis and resolution at the end of the season instead of the switch into neutral with the Sam and Dean stuff. I don't think it was a matter of secondary characters or no secondary characters (I think Cas gave some good Dean and Sam insight, I think ghost!Bobby failed spectacularly but could in theory have given such), it was a matter of having things like the conversation at the end of Slice Girls end up going nowhere at the end of the season.
Re: Extended TV Guide spoilers
Which isn't a Dean gets all the development criticism -- it's that they were doing the insight for Sam through his interactions with Hallucifer. I really think it could have worked, and was working up to a point, as an illustration of a different kind of relationship problem. It wasn't that they were at odds. In fact, the Amy thing generated more communication between them in some ways than we saw elsewhere. It's that Dean didn't trust Sam's sanity and wellbeing (not didn't trust Sam) enough to talk to him directly, as with the Amy thing, so his breakdown of coping (and some of his more positive moments -- his interactions with Krissy represented some healing on his part, I think) was spilling on random people while he turned away Sam's attempts to get him to talk. Sam, meanwhile, was locked in his head and scared of what was going on in his head, didn't want to burden Dean when he could see Dean was teetering, and needed for his own defense the belief that he could cope keeping Lucifer at bay, so he wasn't opening up to anyone at all about what was going on with him or how he felt about it.
That situation itself was a problem in their relationship, and it could have worked if there had been a structure of crisis and resolution at the end of the season instead of the switch into neutral with the Sam and Dean stuff. I don't think it was a matter of secondary characters or no secondary characters (I think Cas gave some good Dean and Sam insight, I think ghost!Bobby failed spectacularly but could in theory have given such), it was a matter of having things like the conversation at the end of Slice Girls end up going nowhere at the end of the season.