I don't know how you can take the Legacy Wagon's shortcoming and say every single wagon out there has a poor A/C system, terrible road noise, etc. Those sound like problems specific to the Legacy Wagon, not problems with the wagon format.
Whether or not it was so bad as to be completely inadequate is specific to an individual model. But it's just a simple matter of physics that it's going to be hard
er for any given AC system to cool a wagon than to cool a sedan version of the same car. It is always harder for any given AC system to cool a space that has 50% more air and 50% more glass letting sunlight in. And road noise going to be loud
er in the wagon than in the sedan, whether or not it's "terrible."
And about leaving perishable foods in your car while you aren't in it, why?! Besides, even if you did want to do that, I'm sure good window tinting would resolve most of that problem for you.
You've never gone to two different grocery stores in one trip?
As for window tinting, even with a heavy tint on the back windows, a wagon's cargo area really can't compete with a trunk that has no glass at all. The passenger cabin still gets hot in a sedan, but the trunk stays nice and cool. Even with tinting, sunlight is coming in the wagon, including through the un-tinted front windows, and convection currents cause the entire interior to be the same temperature eventually.
In the end, it all depends on what you want/need. I see the appeal of pretty much all formats of vehicles, including sedans and wagons.
I see the appeal of wagons too. Tons of cargo space. Sounds to me that you're saying that sedans are inferior to wagons in every way except for not having to tie cargo down, and I think you're ignoring factors that may be important to other people.