I think you would find it to be a 'lack of personal integrity' if the person was doing a change for the worse. What if one of the Backstreet Boys decided to do a rock album, and who knows what if it was a great album too.

If a 'rockstar' turned around and did simple pop '3-chord progression' songs, then that's a lack of musicianship, but if it was viceversa we would think that they are actually "improving". That seems a little unfair.

I commend artist that can completely change their musical style and not care what their fans will think. Either their fans will leave and they will aquire new fans of a new genre, or they will have both fan groups. Which would be great, but it doesn't matter if they truly had 'musicianship' because they are doing what they believe is the best music that they can put out.

How do they have less integrity for staying with a style simply because it will sell better and their fans are used to it, when they want to change it? That just doesn't seem to make much sense to me.