After hearing Marco, and thinking more about the subject, I really think the removal of the economy wasn't the right choice, it was the only choice.
Kunos made a mistake a small studio, like them, can't do: try to get everyone's attention. It lead to a scope too large for what they could handle, and the results are visible to everyone.
As already established, the greatest threat to ACEvo's success, is the original AC. If Evo is to have a chance at thriving, it must render the original redundant. What made the original AC explode into what it is today, was not a extensive career mode, but the fact that it was a highly moddable sandbox. If you didn't like it the way it was, and you had the knowledge/tools, you could turn it into the game you wanted, then share that work with others looking for similar experiences.
It looks to me that Kunos realized that Evo has a better chance if it's a stronger foundation to be built upon, instead of a building that can be somewhat decorated. Unfortunately, a career mode with XP, credits, especially one with connections to multiplayer progression, is incompatible with the kind of moddability expected from AC. Modders would start taking that progression system apart, giving an unfair advantage over anyone trying to do things the "normal" way.