There's a clear difference in Rooney and Ronaldo's approach when it comes to dribbling now as opposed to in their earlier years, in my opinion. They are marked more heavily granted, but it's very apparent how much more willing they were to take on their men in similar situations when they were younger. The difference in Ronaldo now and Ronaldo in 06/07 is massive...it surely cannot be contested.
I doubt they've randomly just become worse at dribbling in a technical sense; it'll be a mental thing. Rooney may have lost his spontaneity when we curbed his aggression, and Ronaldo might have suffered as a result of a shift in priorities (turning his focus more towards goalscoring, rendering dribbling less natural).
These two are such clear examples in favour of the thinking behind that 'attacking the space' thread. Neither were dribblers of the very highest level, yet they always had the drive to take the initiative and drive forward when the opportunity presented itself. It takes confidence and a specific mentality to do that, and I'm guessing these two have less of that now (in regards to dribbling).