I want to make a case that the claim that the PT and OT combined a story about the tragedy of Anakin Skywalker isn’t actually all that ridiculous. I know he isn’t a major focus in ANH and ESB, but the result of his choices ARE. You can have a story about something and still have other worthwhile arcs. Now it’s unfortunate that the PT quality really isn’t where it needs to be to have this all feel unified, but I personally think the original 6 movies can be viewed that way and I personally don’t believe it undermines the great arc of the OT in any way.
As for me. If you have to find a meaning in all of it together (including the ST). I agree with the awesome answer about storytelling.