I am unfamiliar with any large-scale failures of the CCSS with struggling students, but I have seen struggler excel with an approach that emphasizes understanding. Of course, anecdotes are not data, and I'm open to hearing how the Common Core fails our weakest students. I don't think it is perfect, but I do think it is better than any of the alternatives I've taught with.
If we're being honest, in many places in the US, the emphasis on misusing standardized test scores to shut down schools and fire teachers was well under way long before the CCSS. And to be clear, I don't think this makes any sense. But I don't think it's reasonable to pin this on the Common Core, it's just that it provides an enemy that people from around the country can hate on.