Bill Rogers told me five years ago that the transition to a red dot is orders of magnitude easier for a skilled shooter with a refined index. A red dot does not tolerate sloppy anything, and misalignment issues that would perhaps not even be noticed by many iron sight shooters result in no dot visible on a pistol.
The great thing about a red dot is it talking to you constantly about grip and trigger. Anytime the dot is not where you expect it, is an opportunity to diagnose what went wrong and fix it.