I don't like South Park because of that smug, sanctimonious tone either, but my housemates love it and regularly leave re-runs playing for background noise as they go about their day, so allow me to offer that same criticism from someone that has seen every episode multiple times and can offer something "real" to back it up:

The long arc of the South Park plot follows Trey and Parker's political development from bitter, unknown California Republicans with sarcastic, nihilist tendencies to disillusioned Big Hollywood Conservatives with sarcastic, nihilistic tendencies being forced to reckon with the fact that their past attempts at satire have either had no impact or have actually reinforced the perceived social ills they pretend to mock.

Al Gore's portrayal in S22E06 "Time to get Cereal" exemplifies this, even after he is proven to have been right about ManBearPig all along, this later appearance shows him as still being a huge weenie that cares more about being acknowledged as having been right than wanting to actually solve the problem. Having belatedly acknowledged the existential threat, Trey and Parker still can't bring themselves to issue a call to action, and everything goes back to normal after they kick the can a little further down the road.

Thus, the smug, sanctimonious tone has been a constant throughout, as if they still imagine that the greatest sin is caring about things. They're so heavy-handed about it that they lampoon this aspect of their own show in Kyle's "Don't you see," and "Y'know, I've learned something today" closing monologues. Even when he's telling a real political truth, like in the banned S16E06 where the text of the monologue is an admission that terrorism works and the subtext is a refusal to acknowledge their own contributions to post-9/11 anti-muslim discrimination in America, Jesus (representing mainstream American Christianity) gives falsely-sincere advice to the gingers (who represent all minority groups facing irrational discrimination) that they just need to get as violent as the most aggressive extremists so that people will respect them. Which is itself a smug, sanctimonious, and sarcastic way of suggesting that they can never be respected as people, only either seen as lesser or feared as an enemy.