I think the problem with prequel stories is rarely do the creators feel satisfied telling a story at a simpler time, instead they set out to compete with the wow factor of more recent instalments. Enterprise had this problem with crap like the temporal cold war and the very last episode really being a TNG one.
One of my favourite retroactive sci-fi stories is Gundam 0080. 6 episode series set in the middle of nowhere during the final stages of the original series, focused on the Federation building a mildly souped up Gundam for the main series lead and the enemy force who are dispatched to destroy it. A simple story with original characters you come to bond with and some new plot elements that fit in nicely with the existing canon.
Compare this to any other Gundam side story. Tech levels that dwarf even recent series. Elaborate conspiracies to explain how no one knew any of this happened. Characters who are so skilled and powerful, you just wonder why we hadn't been following them.
It'd be so nice if the staff of these kind of retroactive stories could instead play up to the unique charm of these relative holes in the continuity. With Enterprise for instance, I think the best stuff was when they got into exploring how humanity wasn't as enlightened back then and the problems it caused. More impulsive crew members, racist movements against alien cooperation, etc. Just because we know the key events and where that story ends doesn't mean you can't make it compelling by zooming in.