I think what's going on is that the musicians you've liked in the past have stopped making good music, or your taste and theirs have diverged.
There are several musicians that I like some of what they've done and not all. The flaming lips have changed drastically over time, but I still like everything they do. Gov't Mule, on the otherhand, went from a solid improvisational power trio to middle of the road "jam band", and lost me completely.