Erskine hadn't wanted a good soldier, he had wanted a good man. Steve understood why. After all, the Super Soldier Serum that he had created only enhanced the qualities of the one it was given to.
A good soldier will follow their orders, no matter what they are. A good man will do what is right, even if it means going against orders.
Steve had been willing to go against orders to save his fellow soldiers and his friend Bucky Barnes. He had believed that it was the right thing to do, and he still does, that hasn't changed.
But many things have changed. When he crashed in the ice he hadn't expected to wake up, especially not 70 years in the future, but he had. It was difficult, having to learn about what has changed since he crashed. For a long time he didn't try very hard to learn everything new, clutching on to what remained of his past with a vice grip. Perhaps that is where things started to go wrong, his unwillingness to change.
He trusted SHIELD, followed his orders like the soldier he was named as. He trusted them, despite knowing they were spies who knew the worth of secrets. And then, for some reason, he was surprised to find out that they had kept secrets from him. He managed to get over it, trusting but more wary this time. He was wrong to give them that trust.
SHIELD turned out to have been infiltrated by Steve's worst enemies, HYDRA, and no one had even noticed. So, Steve fought them like the soldier he is.
When he was a part of the Avengers, he fought for what he believed was right and protected people. He felt like a good man again and he wondered when he stopped feeling like one.
Erskine hadn't wanted a good soldier, he had wanted a good man. Steve can't help but wonder when he started confusing them.