I can relate to how you feel. I have experienced very similar feelings. I too have been a hardcore Cowboys fan since my earliest memories(SB VI).
What you are feeling now is what we called in the military, "failure to adapt". Murray not returning was a harsh blow but it's done. Right or wrong, we have to move on from there and hope for the best. Letting go is never easy to do. Now we are left with a RB corps that we just don't know can fill the void left by Murray's absence. Facing that unknown takes a certain degree of courage but we can do it. What other choice do we have? Complaining does no good, and it doesn't even make you feel better after you doing it long enough.
Sorry I know what I am feeling and failure to adapt is not one of them. Right now there are reports of the Cowboys looking to possibly move Leary to get a RB a team would not be doing that if they were 100 percent sold on what they currently have. Does not make Jerry any less of a Cowboys fan or failure to adapt. It could very well mean that there are some concerns about the running game.
You are right we enter the season with an unknown at a position that proved to be a strength yet now it is a question mark now. So of course any sane person would have a concern when you go from strength to unknown.
I had said before Murray left for Philly that I would offer him between 6 to 7 mill a year, as we both know Philly offered more and I would have made the same choice the Cowboys did which was to move on.
As for the complaint part? I don't feel standing up for a player who did as much for the Cowboys as Murray did is complaining. I'm not one of those guys who will start belittling players the day they leave and act as if they were not that important.