Actually it was a pleasant surprise that McFadden gained the yardage he did. McFadden's performance was about the only positive thing from the offense that year. I felt that was pretty universally recognized. He just wasn't considered a long term solution because over his career he had proven unreliable and prone to injury. The team drafted Zeke because they wanted a bell cow RB like Murray had been in 2014 to carry the torch for the running game in a balanced offense, and McFadden wasn't that guy.
The "meat on the bone" thing was Joseph Randle talking about DeMarco Murray.
Alfred Morris, like McFadden, was considered a stop gap, not a bell cow, and he wasn't a receiver, which the Cowboys wanted from the RB position.
By the way, the 4.4 is one game, and not a season average. Even in Zeke's rookie season where he averaged 5.1 ypc he had individual games where he averaged 4.4 or less. That's why seasons aren't judged on 1 game.
Even so, 4.4 is far from a poor average. It's not stellar, but it's easily a strong average, especially for a RB that gets keyed on as much as Zeke.