Assent to or defer to? I defer to the pope even in matters where I do not give assent.
Lumen Gentium calls for loyal assent even to the ordinary magisterium. One can do this in a spirit of humility, asking God for the grace and insight to understand why the Church teaches what she teaches. It’s not easy where you have questions and doubts but that’s part of being a faithful Catholic. That applies to teaching, not to disciplinary actions.
I can hope that the capital punishment development might get further theological consideration. I think there could be a healthy debate among theologians about whether abandoning the retributive aspect is right. But for now, we have what the pope and the Catechism say: should virtually never need to be used. Which means we have to focus our efforts on making sure the innocent are defended, that dangerous criminals are paroled to kill again etc. Instead, the bishops concentrate on repeal. That’s a prudential choice on their part, not a teaching point, so I don’t have to agree with them on that.