Pushing hands and routines are both essential to taiji training. And not only do they help to hone different aspects of taiji, I think they help each other too. Practising routines help us to understand how to move our bodies in the taiji way, and to understand the problems we currently have.
Meanwhile, pushing hands helps us to learn how to apply taiji, and experience how the correct application of taiji feels. It is this aspect that I think can then be transferred back into the practice of routines to help us practise in an even better way. Once we have experienced how the application of force in the taiji way feels (through pushing hands), we can keep that image in mind when practising our routines. This "image training" is a way to train our body and mind to move in the taiji way. The image is not just about how each move in the routine is used; it is about how such application of each move will feel, in terms of the contact point(s) and the moving of our own and our opponent's centre of gravity.
For the near future, I will be focusing on this form of image training when I practise my routines.