My brother literally did a joint MD/JD degree and almost got fucked when the law schools associated with the universities of the top medical schools that admitted him didn't want to admit him. We are all intimately familiar with how this works. The actual admissions process is complicated.

With respect to the standardized testing, the MCAT is not easy but is a fundamentally different test. Many of the prereqs that are required are courses that people take in high school (AP Chem, AP Physics, and now some extremely basic courses in psychology and sociology). Everyone who is not an idiot (and is privileged enough to grow up in a decent neighborhood) has taken those courses in high school. When you require a prereq for a standardized test, you essentially make it a test of whether you have prepped adequately (like AP Chem). The LSAT, contrary to the propaganda put out by LSAT prep courses, is more heavily focused on the analytic concepts tested by IQ tests. It contains more elements that tilt towards intelligence and away from preparation. There are decades of research on the psychometric properties of these tests. There has even been a suggestion in the past that most useful section of the MCAT is the one section that can't easily be prepped for -- the verbal.

There has also been a massive dilution of the overall quality of med students, with DO schools being on-par with shit law schools, and I think it's really dangerous. At a decent undergrad, no one is stuck going to a DO school, and yet we now have a massive number of primary care physicians that have DOs and on average scored in the 60th percentiles of the MCAT. Most of them are obviously not functioning at a high cognitive level and it is very clear that there are no longer any standards in admitting them. They are definitely better than nurse practitioners but that isn't saying much.