This. What you learn during your preclinical years and what you study for boards does not translate into the everyday practice of medicine. During 3rd and 4th year rotations is when you actually start to learn how to care for patients; how to act like a doctor. You basically learn how to gather a history, perform an appropriate physical exam, and come up with a plan, which are the fundamental skills you need as an intern. Your clinical years are arguably the most important aspect of your medical education.
You also learn some procedures on your rotations, but it is somewhat of a hit or miss process depending on the attending/residents you are working with and what rotations you choose to do. I'd recommend doing a month of ICU, a month of surgical ICU, and a month of anesthesia before you graduate. Not only will you feel comfortable treating very ill patients but you will also learn a lot of useful skills, such as mask ventilating, intubating, and central line placement, which are skills many interns, residents, and, even attendings, are deficient in.
As a 3rd year, you pretty much can only do electives at your school's affiliated programs. As a 4th year, you can do electives anywhere that will take you. Most, but not all, hospitals take DOs. You can visit the hospital's webpage and click "visiting medical students," or something similar, to see what their requirements are for visiting rotators. Also, many hospitals use VSAS, which is an online application service for visiting students. I used this service to set up my elective rotations at university hospitals. You could make a log in and see which electives are open to DOs.
https://www.aamc.org/students/medstudents/vsas/