This doesn't mean we won't still use all of the other skills and resources available to us. It means we have more and sometimes better alternatives to draw from, and we need be selective, choosing the most effective for any required task. Projects are so time consuming. The idea of doing a continuous series of projects or multiple projects in different subject simultaneously would indeed be too time consuming and as well as overwhelming for students. Although this is an exciting way for students to learn.
Planning is always the key to success in teaching.
Collegial planning would avoid duplications that could arise. It is important that two teachers teaching different subject to the same class check that they don't start projects during the same time frame. Many students would find it too much to be doing more than one project at a time. Individual teacher planning is critical for efficient use of class time. By planning ahead we can cover objectives from multiple curricular topic simultaneously, thus using time economically.