Thanks for your feedback!
Production lines (and the whole production system) are one of the first things we implemented when Prosperous Universe came to life around five years ago. Back then it was just Martin and me and we had no dedicated game designer. It is obvious that this shows all over the place.
Around 2 years ago, we started the 7th alpha test (the current universe) and made the decision that with this alpha we want to concentrate on features, mid- and end-game content. During that period Fabian joined as a game designer and started to work on these new features. The alpha test was never intended to run this long and as the time passed the player got bigger and bigger companies and managing them became really cumbersome. That is why we recently asked about your favorite quality of life improvements and started to implement a few of them.
We could have promised the perfect production system instead, asked for the players’ requirements etc etc, but “perfection is the enemy of progress” as they say. We’d rather implement and test new game mechanics than re-iterate over and over the old ones to make them perfect. This doesn’t mean that we won’t improve existing features, but a whole re-write binds a lot dev resources and we don’t have that.
Often times, as many of the long time players can tell you, we only implement the bare minimum of a feature to see how it works and turns out. Later we come back and add the missing parts to it: building repair button, test flights, warehouse extensions, to just name a few recent examples. The reason for that is that we deal with a lot of constraints and not because we are in a secret game-dev-club that wants to make players’ lives miserable 
I hope that explains at least a bit why things are as they are!