It’s mostly the airport and local regulations that prevent plane cooling today.
If a plane uses ground air, it’s usually only a few degrees cooler than the plane. For example in F, if the plane lands and has all the windows shut and is 80F which is too hot already, they hook up to ground air which will blow in 70F to 72F air. You aren’t cooling a plane in the direct sunlight with 200 people breathing with a 10F max temperature differential. It’s just not possible.
In the old days, you’d drop the APU and run the PAC which would actually air condition the air and keep the plane cool. Even in the hot sun. But this cost about 20 to 30 gallons an hour and was a big noisy stinky polluting engine running anytime the plane was on the ground. Plus the maintenance of the APU and such for hours run.
If you travel outside the US and Europe, the APU and PAC is still used as normal. But it is not environmentally friendly. However neither is the actual giant plane. 30 gallons is a leak for the hour on the ground compared to what’s burned just to get air born.