I've always considered it like this:
Tony Romo was the exception. But don't be confused. Romo also has Jim Nantz to navigate the show and give direction from within the booth so the entire product appears more polished.. Nantz sets up Romo well for a lot of his slam dunk analysis.
Also Tony should have had a more natural transition by default just based on our team dynamics.
Tony was the fun, hat backwards, charismatic guy, came from nothing, related to everybody and always sounded conversational in interviews. Witten was the opposite. Hard hat, lunch pail, 9 to 5 straight shooter. Didn't participate in pranks in the clubhouse. Business, corporate.. still a leader, but a different type of communicator.
There's no way ESPN could have thought a guy doing that role for 15 years would flip a switch and be good in the commentary booth without a veteran partner or some sort of improvisational skill. This is what you should get 10/10 when you put someone on Live TV with no script and ask them to wing it. It just seems like if they wanted to recreate the Romo magic, a guy like Booger McFarland was the true pick but they needed the former Cowboy "formula" to help their ratings and added Witten and this is the result of that decision.