The problem isn't that it has had it's day. It is that it hasn't been updated properly. While it is great to still hear about life in 1904, 1927, 1948ish, and 1999, it really wasn't ever meant to stay those dates. The first three was years out of decades that the audience still remembered vividly. Now it is impossible for someone to remember living the days of the first act, you have very few people who remember the days of the second act, and our grandparents and great grandparents only familiar with the 3rd act first hand. While most of us can recall the days of Act 4, it's truly an accurate depiction of the 90s so much as a depiction what the end of the 90s was supposed to be like in the future.
The building and ride system haven't aged well either. Browse YouTube and you will find lots of videos of Carousel of Progress acting up. Guests simply leave the theater leaving guests to watch the same scene multiple times until it gets to the point that they literally dump the building and have to start all over.
CoP might be getting a small minor refurbishment in the fall, but they really did miss out on an opportunity completely restore it for the 50th of completely redo it for a new generation.
I've said it a few times on here, but all they need is a sponsor like Apple or Microsoft to come in and the focus needs to be placed on how the computer has change home living over the years vs. electricity.
Act I - 1955 - Electronics and modern appliances are really starting to ramp up in home living. Futuristc thinking is on the rise. We have lots to reference in pop culture with Disneyland, rock n' roll, etc.
Act II - 1976 - Both Apple and Microsoft were born in this year. America was celebrating the bicentennial, perfect for the 4th July references of this act. Home living features lots of new electronics, more and more of which are leading us to personal computers.
Act III - 1999 - The height of the dot com era, personal computers and digital technology were at a high, but still had so much more untapped potential. Video games, television, satellites, cell phones, the internet, and even probes being sent to Mars. The late 90s were another time of futuristic optimism.
Act IV - 2025 - We've come along way since 1999. The internet is no longer a baby. Cell phones are smart phones. Technology is king with digital paper, 3D printing, home automation truly becoming reality.
Carousel of Progress would have lost some of the museum factor and nostolgia of almost being exactly what Walt creating, but in it's place, his spirit would live on with a new show that would reengage audiences on a trip through their own lives and not some much of a century before.