Those two statements aren't at odds with each other.

For example, there's a great abundance of resources to learn about music theory and such too, the average person doesn't know such things because they aren't interested.

no, it says the opposite, that there is growing interest in bringing it back into curriculums in various states. but that's aside from the point that the smithsonian making a tutorial on reading cursive would just represent an additional resource, of which we are not lacking, to learn. whether or not we teach it is different, but finding a resource to learn is not hard.

I find the article's conflation of two topics involving cursive writing ignorant or disingenuous to the point that I almost wanted to respond with my own comment on that itself. If you study cursive writing in class, you are likely to learn simple and standard letterforms like Palmer script.

But the task requested by the National Archives is more akin to paleography where you can expect each author or work to have their own (region-based/family-based) handwriting that requires decipherment, even for experts. You may have encountered a coworker or schoolmate's indecipherable chicken scratch print writing; that is what you should expect, only cursive.