As for the change in singing styles...
I'm with DR Jason on this one... It's the whole evolution of popular music in general. -Remember when "show music" actually was "pop(ular) music"? All things change, like it or not, and you can like it... or not. Yes, microphones - and myself

- can be blamed for a contributing to the "problem", but as long as "we" continue to "not go" to a show just because we think we may not like it, well... Then that truly will be the death of musical theatre. If there's no audience to play to...
Heck, even operatic performance standards have changed over the past 50 years - even over the past 20-30 years. Yes, there are still some admirers of the "stand and sing" school, but most of today's audiences want to sense some "acting", some real emotion - not just painted on tears and worry lines.
And I believe DR Jason and I were both very surprised at how much we "got" and liked Michael John LaChiusa's newest,
See What I Wanna See. And it actually demands a couple of different vocal styles from it's performers: everything from a jazzy-cabaret performance to some quasi-operatic singing to gentle ballad delivery.
Well... I could ramble on and on... And I sort of have already, so...
Next!