There is some truth in that; if you aren't doing well, something needs to change--university, major, time management. However, I do think that gpa is valid to some extent. Wherever you go, you should be able to get a 3.3-3.5 by graduation (after the aforementioned changes, if you need to make them), and that is usually the cut-off for considering applications/inviting students for interviews. Just do well on the MCAT and apply to schools that are in your range and have the niche you're looking for academically and with respect to extracurriculars.
That being said, major in something(s) you enjoy, go to a school you enjoy, and don't be afraid to take some risks. Personally, I would be miserable taking classes that didn't challenge me to think, and I never did well in introductory classes/"easier" sort of classes. I needed the physical chemistry and social philosophy classes to supplant the pre-recs and core classes that didn't cover much new material. If you're that type of person, don't try to take a bunch of "easy" classes or go to an "easy" university where your advisor/classmates won't understand that constant need to learn. Even at a fairly esteemed program, it was difficult to find others who related to my desire to learn deeply and broadly in many areas and my passion for some of my fields.
You will also be better prepared for medical school by taking upper division classes and challenging yourself--several of my classmates had issues passing when all of the material was new and there was little time to learn it. I think that even the people who don't need to be intellectually challenged all of the time would benefit by taking a course or two in something challenging. That's what medical school will force you to do (try anatomy in less than 2 months or a course that's only 2 weeks with a final), and you need to know that you can do it before investing so much money in your medical education.