Well, maybe.
ALL SHOOK UP, while all Elvis music, had a new and fresh sound with excellent orchestrations. Plus all of the arrangements were different. It was truly a different beast.
If MAMMA MIA! were as terrible as XANADU (or if it hadn't become a huge sensation) then I could see your point - but it's one of the best selling cast recordings of all time.
BUDDY, I know nothing about.
And JERSEY BOYS - sure - but again, rave reviews, sold out, etc. etc. It made sense money-wise.
I'm not saying I wouldn't buy a XANADU cast recording - I do like the music. All I'm saying is that I don't know if it would be financially successful. That's what it comes down to.
"If you are going to do something, do it well. And leave something witchy."
-Charlie Manson