I may be able to elaborate a bit on that. It seems when a band finally gets accepted by a large amount of people, those people are the ones that made them what they are. The people don't like drastic changes, and bands that usually try to re-define the face of music after a few successful albums, fall by the wayside.
This seems to be true with just about every band in existence. You're liked for a certain sound, and people want to continue to hear that sound for a while. But after a few albums of the same caliber, the band grows and matures in their songwriting. They'll lose some fans, but will gain others. It all depends on how drastic the change-over is.
In Metallica's case, I think their change was for the better as far as survival goes. Though I'm not and never was a fan of theirs, I really appreciate them for what they were, and what they are now. They paid their dues, and sold quite allot of records in the past especially when there wasn't radio airplay. So that to me in itself is reason to at least appreciate a band even if they aren't my thing.
People will call them sell-outs and that is what bothers me the most. Why I wonder? Because they wanted to make a few more dollars and appeal to a wider audience? That's not selling out to me, that is business......but only if it is the way you wish to go. Yes there are bands that sold out for the sake of selling out, but again...isn't that their perogative? To me, if you are maturing and all of a sudden you seem to be writing more hit like commercially acceptable material, that is fantastic and it shows growth. Any hard working serious professional mucian will admit to that.
Van Halen....one of my all time favorite bands for example. All the older stuff was more attitude, more guitar playing and a cool party vibe. What happens when you put out 6 albums of that stuff? You start to mature a little and think differently. You try and test the waters a bit. I loved VH with Roth, but the bottom line in my humble opinion is the songwriting improved drastically when Hagar joined the band. Ok Eddie wasn't as innovative and didn't play like the maniac he once was, but you get to a certain point of your career and you grow....sometimes you change.
Writing a song with an awesome hook is something that is an artform all in its own. People call it sellout, but then again...most of them that say that are musicians, and if you cater to them, you usually don't sell as many records. If it sounds good, it is good, there are no rules in rock n roll. And if you can write hit material, your not selling out unless you are record company manufactured. Hit material and orchestration takes as much time and creativity as progressive off the wall stuff. In the long run with music today, the answer is survival and you do what you gotta do to put food on the table. Take care.