My feeling with math is that moving on too soon is disastrous. If you move past a subject without having grasped it, you don't have a good base for the next subject. This compounds, and the explanations stop making sense.

At that point people are trying to help you but saying things to you as if you are stupid, but you still don't understand. That really sucks, so people get afraid of math. Avoiding it, and nodding when asked "do you understand" when really they do not. This is hard to fix because you need to go back to the point they did not understand, but the fear and pain makes even teaching that a lot harder to fix as well.

My feeling is that most people should be able to understand algebra. However, I think that requires a very deliberate and personalized approach for some people. Certainly with collective classes, if you go at the speed of the slowest student there will be slow progress and a lot of people who are bored and mentally check-out.

If any approach is going to work for people who have real difficulties, it needs to be small-scale personal teaching, and it needs to come with trust. Someone needs to feel like they can keep saying "no I do not understand" without disapproval, disappointment, or frustration from the tutor.

This is so true. I'm Black and attended one of the worst performing elementary schools in my city for the first four years of school, which gave me an awful base for my math learning when I was finally transferred to a much higher performing school in a Jewish neighborhood on the other side of the city, not to mention high school and college. Only when I started working in programming did a lot of algebra and trig click (probably helps my first junior role threw me in the deep end working with linear algebra and trigonometry in animation and was lucky to have a senior around who chose to take on a mentor role). Math in public schools is basically magical spell incantation and it appears to most kids that you either have "it" or you don't. Math is a subject I believe requires long-term work that doesn't easily fit into the grade pass/fail structure of school, but then again a lot of aspects of mass education are fundamentally broken.