Writer is complaining that the engineering design projects start in the junior year of the curriculum at Princeton (note that ABET accreditation does require engineering design course work as well as engineering science course work).
That can be a rather traditional and efficient way to organize the curriculum, since math, natural science, and engineering science course work is often the prerequisite for engineering design course work that is typically done in junior and senior years. However, it does mean that an engineering student is not exposed to the engineering design process early on, which can affect how s/he views engineering (it obviously reduced the writer’s enthusiasm for the subject, apparently leading him to change to philosophy).
As the writer mentions, some other schools have added lower level engineering design course work to the frosh and soph years of their engineering curricula to help confirm students’ interest in engineering (or let other students know early on that engineering design is not really for them).
Princeton’s ME is described at http://mae.princeton.edu/sites/default/files/MAE-UG-HANDBOOK-Fall-2014-V4-Class-of-2015-and-2016.pdf ; page 14 shows the soph year curriculum. Note, however, the “science first, design later” curricular organization is not unique to Princeton. Some other schools have similar curricular organization; see http://mae.rutgers.edu/sites/default/files/uploads/MAE_CURRICULUM_LATEST.pdf for an example. In contrast, some other schools include design courses starting frosh year; see http://www.rowan.edu/colleges/engineering/programs/mechanical/AdvisingWorksheet.pdf for an example (the “clinic” courses include design work, according to http://www.rowan.edu/colleges/engineering/clinics/ ).
If this is a concern for a given student, looking over how the curriculum is organized for the desired engineering major(s) would be helpful in selecting among schools.