If you don't fulfill your promises you are a liar. It is that simple. Presidents/MajorityLeaders throughout history have found ways to pressure recalcitrant members into passing important legislation. There are also important things Biden can do on his own without the Senate such as abolishing student debt. The Republicans have shown the ability to do this with their caucus time after time. The Dems refuse to do this. Some of this is incompetency but some of it is absolutely because they are unwilling to change.