We do have a term: slow to learn to read. We don't need dyslexia or some more specific term unless those terms can be used for better treatment. In this case dyslexia is too specific: kids who don't fit the definition are being actively harmed because the treatment would help them just as much as it fit those who it helps.
It may well be dyslexia (or a more specific term) may mean some other treatment can be helpful only for those who have it, and not for the general population of poor readers. This hasn't been suggested (to my knowledge), but it is possible.
Though I will note that the definition of Autism has gotten broader over time as treatments have been discovered to help kids who didn't fit the previous definition.
It may well be dyslexia (or a more specific term) may mean some other treatment can be helpful only for those who have it, and not for the general population of poor readers. This hasn't been suggested (to my knowledge), but it is possible.
Though I will note that the definition of Autism has gotten broader over time as treatments have been discovered to help kids who didn't fit the previous definition.