Like, I get it. I get what they’re trying to do with this prequel, and I understand. I do. But that doesn’t change the fact that I think it’s unnecessary.
We already know most of the important parts of John and Mary’s story.
We’ve already seen their earlier days, where they were just dating and happy (ish). We’ve seen what Mary’s life was like back then and we know a cupid helped get them together because destiny and shit. We’ve seen the choice Mary is forced to make to save John, the choice that sets in motion the entire series. We see them a little later on, when Mary is pregnant with Dean (?). And we know what happens to both of them after Mary dies in the pilot.
This is just my personal opinion, maybe others disagree. But I just don’t need to see anything else.