I think they look much more elegant than a lot of recent fashions but so impractical - a lot of ladies fainted on a frequent basis as their internal organs were crushed by the corsets needed to obtain this silhouette and their ribs couldn't expand sufficiently to breather properly.
Also because fabric was expensive and a dress like this takes yards and yards and yards of fabric, even the very rich didn't own many dresses so they would have smelt. No doubt about it.
Then there's the practicality of how you would get through a door frame - a lot of the wide skirts meant ladies had to sidle sideways into rooms!
As for being too hot, I don't think that would have been a problem - Victorian ladies wore these dresses with MANY layers of petticoats underneath in India and other hot countries that were part of the Empire and didn't seem to suffer unduly. To a certain extent, being covered up is cooler than having uncovered skin in hot countries.