I'm thinking Caprica and BSG actually made it harder for this new series to succeed, because the target audience would consist mostly of viewers of the other two series. At this point I'll venture that most of us don't really care how the story started anymore (some mob stuff, sports, corporate takeovers), and don't really care for how it ended up (pointlessly and 150,000 years ago), so we're very unlikely to find ourselves emotionally investing in characters and events that happened somewhere in the middle.
Yup. Interquals have it the worst. At least in a prequel, it's usually wide open enough that you can choose any starting point you want. And you can make it different enough from the original so that the interest can become about how the story got from Point A to Point B and the twists involved.
In an interqual, the started point is limited and it the situation can only be so different from what happened before or after, especially when we already know what happened in between. The series is completely boxed in, locked in both directions.
That's probably why ENT didn't take place between TOS and TNG. We already know what happened to the Enterprise-C, so that rules out that ship. As for the Enterprise-B: you'd be stuck with the TWOK uniforms, an Excelisor-class ship, and an Alpha Quadrant not too
different from TNG. The Klingon Empire wouldn't be able to afford war, which would make them effectively neutral, the Romulans would still be up to their old tricks, and maybe you might have the Cardassians around. That's about as much room as that type of series would have to move around in. It would be a TNG set-up without the TNG/DS9 backstory and with the TOS movie look. Nothing new or fresh about it. It would've looked more at home in 1991 (though redundant) than in 2001. I didn't care for ENT but, if they wouldn't go forward, at least having the show set in the 22nd Century was a novel idea.