>>48428561So many cool things you can do with seasons that aren't that dramatic like give mammal pokemon more fur during fall/winter, or make pokemon like Snorlax and Ursaring slightly fatter in the winter and slimmer in spring.
You can give clothes wearing mons like Throh/Sawk slightly warmer outfits in the cold weather.
It doesn't even need to be plants with large variances.
But alas Gamefreak has zeroninterest in doing above the bare minimum.