FIRST THING TO UNDERSTAND: Baroque music is really really fucking cool. You could see it as a reaction to more constrained medieval/renaissance music, which was often obsessive about certain musical rules. Baroque comes from the Portuguese barroco, "an irregularly-shaped pearl", and was actually used as a criticism meaning something very weird, dissonant, overly extravagant, etc. It's seen as very structured but is in fact a collection of big ol' "fuck yous" to the previous era of musical structure.
SECOND THING TO UNDERSTAND: Vivaldi was really really fucking cool. He was nicknamed "The Red Priest" as a young spicey ginger, and for many years he was the violin maestro at a combo orphanage/music school for girls. He wrote a zillion works specifically for the girls to perform, coached them in music theory and instruments, and helped many of them launch esteemed careers abroad. Also the board of directors hated him and kept firing him and then realizing they needed him and bringing him back, for reasons completely lost to history, but probably related to his spiciness.
THIRD THING TO UNDERSTAND: "The Four Seasons" is really really fucking cool. It's written to accompany four sonnets with super vivid imagery including sudden spring/summer storms ("Thunderstorms, those heralds of Spring, roar, casting their dark mantle over heaven!"), mad drunken revelry, the chase of hunting dogs, slipping on ice and eating shit, etc. When you hear it played properly it's very much not "this pretty song kinda reminds me of spring" but "oh wow I can hear dogs barking in the viola section, chirping birds in the violins, a summer storm wrecking the fuck out of my grain, and dangerously crackling ice!"
FOURTH THING TO UNDERSTAND: "The Four Seasons" is rarely played in the spirit of its time. This is Mozart's fault. Well, not really, he didn't tell anyone to play it wrong. But he did give rise to a cult of strings players who play in a very "Mozartian" style - light, pretty, clean, effortless. And for some reason (ahem. some reason i won't go into as this is long enough), this playing style has become the predominant mode for The Four Seasons. Which makes it sound like light, pretty, clean, fancy music.
As we covered above, it is baroque music, so it is not any those things! It's weird and crunchy and extravagant, with musical affectations that would have been considered revolutionary at the time. If you're playing it in the baroque tradition you're also going to be adding your own ornamentations and expressions. Bringing your own weirdness is encouraged in baroque music.
Basically, it's a crime that everyone sees Four Seasons as "fancy music that plays in movies when rich people are onscreen" when it was written by The Red Priest Who Ran A Girls School For Orphans When That Was Very Much Not The Done Thing And Pissed Off the Board At Every Opportunity, and written during a musical period that history has classified specifically as a fuck-you to "pretty and clean and fancy."
