Didn't he also tell him not to marry that girl?
Regardless, seasons 5 & 6 being kinda average and season 7 being more focused on epic scale and action instead of character development and plot...it's easy for me to forget how well GoT handles plot, characters, storytelling, and world building. There are so many main characters with their own growths and regressions and it's done very well. Poor Robb...put into a position he was too young for and was a victim of his own inexperience
that was Cat.
Robb basically went "Okay." then married her. in the first few episodes Carstark said that the war was lost the moment Robb did it.
see... yes. but no. Robb was smart. remember he won
every battle, but lost the war, but the reasons why was because of "Starkism" that i've called it. It's true that he was able to see issues that were arising but he never saw the game from their eyes (like Ned and Jon, reasons why all 3 ended up dead).
for example.
he says he'd do anything to get his father
Cat goes "you need to marry the Frey girl."
Robb says yes. and a good chunk of the reason why he didn't was because he thought they were all plain and ugly (remember everyone's reaction when Edmure saw Rosalyn for the first time? Even Robb was like 'whoa." and Walder had that look).
Then he meets Talisa and basically everyone's like. have your fun but keep your eyes on the prize. Cat and he talked and she pointed out that she never chose her father, nor loved him but she grew to love him, and Ned her. It was literally in one ear and out the other.
Then where he lost people was
1: Cat letting Jaime go.
2: Not understanding how mad people were about that (he kept saying it, but he never truly comprehended it)
3: Not allowing the carstarks to satisfy their need for justice.
4: Not explaining to people
what his plans were (see: Edmure, Mountain and the Mill).
5: not understanding/not caring how mad Frey would be about slighting him (though the Red Wedding wouldn't have been in
anyone's world. considering it broke Guest rights).
The think with Starks is that they expect everyone to play the game the way they view the world. (which as was pointed out, the world as everyone knows it is falling apart so maybe...). but the utter lack of communication or not seeing how other people will assume things (or think how they figure it out they'll be "well ill be honourable).
He also didn't have the "fear of God" that Tywin commanded (this is due to age imo). Tywin would have done something to shut up Carstark about vengeance (though, had Carstark had done what he had, Tywin would have taken the long game in punishing them).