Okay, a distinction needs to be made.
Technically, the map does work. You could theoretically play an entire match on it.
However, the layout is just not meant for PvP. It's meant for MvM. You haven't done enough to change it. And the amount of work you'd need to do to change it would make it not a MvM map or at all related to Mannworks anymore. It doesn't work on a higher-level design standpoint.
When people say "it doesn't work" what they mean is "this map is not meant to be for PvP". I mean, what have you benefited from making a 3CP map out of Mannworks, other than a bunch of free work done for you detailing wise?