I make fun of it, and I have 2 degrees. But I am in my 50's. I had 2 kids that got hit at the beginning of it. The ridiculous thing was what you pointed out, it should be acceptable for people to learn how they learn best. My daughter was very very good at math. Did a lot in her head. She is in college to be a math teacher now (maybe English, she's changed a couple times). But she would do her assignment, much faster and more efficiently than common core taught, and get a bad grade with the right answer, wrong method. She got grades overturned which helped her keep her 3.95 GPA. But one class she had every answer right and was riding a B- because she wouldn't do the common core method. That was absolutely ridiculous. Watching her slog through algebra assignments was painful, especially when she was saying "the answer is -13" before she even started writing out the grid or whatever. And of course she was right.
It made math more difficult for my son too, even while he was not very good at math. He would still say "isn't it easier to add it across" rather than grouping and stuff. He got ok grades because he showed the work, but he also told me that getting into the real world math just does not work that way.
It's a joke. I think it might be a good tool for certain circumstances, or as an alternate method, but making it the end all be all was just stupid.