The Nexus would have been the most sought after weapon in the galaxy

The problem with some writers is that they never really think of the consequences of the story elements they create. With Star Trek Into Darkness they had someone teleport himself with a handheld device all the way across the galaxy. That would have turned the galaxy on its ear as every power would have wanted to get their hands on that device to save on the power needed to build and fly ships and for military purposes to beam armies any in the galaxy at the blink of an eye.

With the Nexus you have this floating ribbon in space that you can enter and exit at any point in time. You could change history a dozen times over. Klingons would jump in and jump out and attack the whole galaxy hundreds of years ago in the past. In the Next Gen timeline Romulans, Cardassians, and the Federation would be eyeing each other and the Nexus and there would constant fear of an operative going in and coming out in the past to change history or vice versa - go into the future then back to the present to warn about upcoming events.

The Romulans and Cardassians would have far less concern about unimportant planets and would destroy whole systems to manipulate the ribbon's course to their favor while fighting each other like mad dogs.

Meanwhile the depressives and addicts of the galaxy would be seeking this nexus out by the billions. You'd have space filled with people tracking this ribbon looking for their personal Nirvana where they could live forever in happiness. Meanwhile societies would be in jeopardy as so many rush off on wild chases to catch this magical ribbon.

Instead this plot device to get Kirk and Picard together just floats off into space and we never hear from it again. Bull!