Big Ant can certainly be blamed for not including co-op out of the box: admittedly I've no idea how complex that is to code but it's a standard feature and it was odd it was not in originally.
Beyond that, all they have done is committed to deliver the feature, and have never given a timescale. Anyone purchasing the game on the basis of a feature they know isn't in the game and has no timescale for delivery has nobody to blame but themselves.
The feature was delivered on PC as one of the first updates of the set that are to be termed "patch 3". That it isn't yet delivered on console is partly because of the vagaries of the platform submission but more especially because of the time spent by Big Ant delivering extras that were not promised: better AI field settings, better AI running, better AI innings pacing when chasing, additional shots.
I've had my differences with
@Ross but I'm not inclined to consider it his "fault" that a feature he provided no timescale for has taken a bit longer to deliver than a couple of cry babies expected because of time spent providing big, unpromised improvements for free.
You bought a game that you knew didn't have a particular feature, and no specific timescale for delivery. It was your mistake so man up and admit it. If it's the biggest mistake you ever make, you'll have had a good life.