obviously, I would have no problem with that, but there's this thing called reality that gets in the way. i think you're seriously undervaluing the sound of Pet Sounds. it was a very very calculated thing, and in many ways was "lightning in a bottle", strokes of unconscious creativity.
1. the complexity of the arrangements. if Brian Wilson attempted anything of that magnitude again, he would have an aneurysm moments later. the man is a paranoid skitzophrenic with tardive dyskinesia, and even if he wasn't hearing voices, he's done enough cocaine to severely hinder his creativity anyway.
2. the session players involved. the wrecking crew were some of the finest musicians to ever be assembled together and had a whole lot to do with the creation of Pet Sounds. Tony Asher also had a lot to do with Pet Sounds lyrically, and he hasn't been half that good since.
3. they're 70 years old. pet sounds was almost 50 years ago. 2 of the 3 Wilson brothers are dead.
it's a nice dream, but it's like hoping the next Paul McCartney sounds like Sgt. Peppers. it's just totally unreasonable.
let's just say what it really is, and that is, it's a miracle that Brian Wilson, Mike Love, Al Jardine, and Bruce Johnston are even able to still make any music at all together.