You are right.
Textbooks does make you a better doctor, but you have to pass to become a doctor.
Because, Knowledge = passing exams.
Medicine is too wide and you can't know everything, especially not at undergraduate level.
At this level, focus on your lecturers slides, Pdfs and past questions so you can pass your exams.
In your spare time you can explore textbooks but only after you have assimilated your slides.
Take care.