I was watching X day: the invasion of japan last night on Disc. They wer etalking about the invasion of Okinawa alone comprising of a fleet of 1500+ ships. There will NEVER be an invasion of that scale with the current threats we have today. It's just not feasable. Back then you needed the bigger guns at you disposal. Today we have superior air power with pricision accuracy.
It's sorry to say but unless it's a CV the big ships are "obsolete"
The Marines now want an "over the horizon" capability of sea based invasion an that's were the CV22 comes into play. You will still have the amphib vehicles and such but it isn't just 200,000+ GIs hopping in higgens boats and making a mad dash to the shore line anymore.
That's just not the way it works, it is now a full spectrum response of aggression and precision.