The state of Alpha 14 is exactly why we've taken the time to do these major overhauls. We hit a major performance bottleneck with physics being coupled to Unity.
The update is taking a long time for two reasons. First, there's been about 3 years of development time built on top of the old physics framework. So we've needed to go through and update, or rewrite sections of the code to work with the new system. That's been no small task, and has taken more time then we initially estimated.
Second, we can't release while physics work is in progress. The game just isn't playable in that state.
The good news, is that regular development has continued on. In many ways, the new release is more like two updates in one at this point. I hope you'll find the new update was worth the wait.