What did "EPCOT" originally stand for? Experimental Prototype Community Of Tomorrow (ie Utopia)... What was the original design of Future World... Futuristic pavillions designed to immerse you in a general theme of technologies:
SE : History and Future of various modes of communication.
UoE: Origin of fossil fuels and other advancements in energy sciences
WoM: History and Future of various modes of transportation.
JII: The Original Dark Ride... With the 2 Original Epcot Characters (Figment &Dreamfinder)... Illustrating in a fun way how imagination is key to innovations.
The Land: Environmental and basic nutrition issues
The Living Seas: The origins of how life came to be on earth, through oceans. And how our future demands that we explore this world as much as space... All in a sea base setting.
The Communicore: Various applications of todays technologies displayed for our enjoyment.
And last, but not least, Horizons, the embodiement of "EPCOT" and the ride that united all of these concept in a totally immersive ride.
Although, I agree that TT isn't lame, is a thrilling ride and is less dated than WOM, and most of the rides I mentioned... The question people should really ask themselves... How does it fit in "EPCOT"?
From my point of view, I don't see the history nor the future of transportation in the crash test dummy's seat.
Does Mission Space encompass all that Horizons represented? No it doesn't.
These are good thrill rides in a futuristic setting and nothing more... They're not made to make us think or dream, in the extent of their past counterparts, of a utopic society. The proof is this simple fact... You could put them in the Magic Kingdom's Tomorrowland and they would fit right in there.
Nemo's living seas... Is now just an Aquarium themed with Nemo and friends. A good idea that could fit in Animal Kingdom.
Soarin'... Which I love, could fit anywhere.
So... "What should NOT have been replaced"... At Epcot, that's easy, the answer is "EPCOT"... Be it because of sponsorship, or other economic factors... The bottom line is Disney should have decided long ago that the basic idea of every one of these pavillions should have been upheld, revamped and maintained in limited partnership with their sponsors.
Basically, they should have accepted to lose a few $ to maintain this park's unique identity.
P.S: I just noticed that the last entry was in 2005... Better late than never!