Star Wars is about Luke Skywalker, not about how his Dad became evil.
In fact Star Wars is about many things. It’s both Luke’s story and Anakin’s story. ROTJ has really been made that way in 1983 when Lucas was developping his PT ideas. So ANH and ESB are Luke’s story, but ROTJ is both Luke’s and Anakin’s story.
The issue with chronological order is that they could not want to complete the saga if they begin with the PT. If they really want to, add the “Clone Wars” cartoon network movie which fuels everything that’s missing in the movies. That way you get an overall PT better experience.