Actually, not nuts at all. Although North Americans tend to associate gondolas with ski resorts, these systems are operated in 95 different countries across 6 continents. And, some of those countries are in sub-tropical climates similar to Florida. Gondolas with air conditioning are the exception, not the rule.
More about Dopplemayr (the manufacturer):
https://www.doppelmayr.com/en/the-group/facts-and-figures/
The gondolas will have heat resistant wraps that will reflect sunlight. Additionally, slatted windows and constant motion will provide air flow.
The good news is that no one is going to force guests to use the system. Instead of hopping on a gondola at Epcot to return to your resort, you can take a bus from the main entrance. Just keep in mind that you may end up waiting outside (with zero air conditioning) at the bus stop for longer than the time you'd be riding in the un-air-conditioned gondola.
(Note: The status of buses from "gondola" resorts have not been officially announced. Some claim buses will cease; I firmly believe they will still run. Although, the frequency of buses will probably be reduced.)