it's a bit of a downer than their one of their proudest moments is performing a kind of music that they no longer feel compelled to produce.
heh. They went from a death metal with progressive tendencies to a retro band with some distorted guitars every once in a while (but mostly just acoustics).
I see what you are saying but bands evolve all the time in pretty drastic ways. Bands like Anathema, Katatonia and the Gathering, made bigger stylistic changes and became better bands for it. In terms of the wider frenzy surrounding new Opeth, I get that people don't like the music Opeth is making now (based on the 3 albums its a mixed bag for sure) but I don't understand why so many always bring it back to the stylistic change. The stylistic change itself has nothing to with the quality of the music, its the songwriting that determines its worth.
I'd like to provide a counterpoint to that. The other day I heard a bluegrass version of Elton John's Rocketman, a song I like. It has the same melodies, harmonies, chord changes. It follows the same structure. But done in a bluegrass style. I did not like it as I don't like bluegrass music. The pacing, the vocal inflection, the instrumentation do not satisfy me musically.
I would venture to say that the style a song is in indeed does have an effect on whether it will be enjoyed by any particular group of people depending on if they enjoy the elements of that style or not. When a band decides undergo a style shift, that alone can and clearly has produced a reaction from the fans.