Oh yeah, it doesn't bother me, and usually Nintendo's good at matching a character to a course that makes sense. Wario and Waluigi being loud, chaotic and obnoxious fit well with various stadiums and arenas, Yoshi and DK usually get jungle-themed, mountainous areas, Koopa Troopa Beach always made sense to me, etc.... really the only one that truly struck me as "hey let's slap a character on this and call it a day" is Toad's Turnpike. And when you're one of the coolest Mario Kart courses of all time, you can get away with that sort of thing. <3 Toad's Turnpike. I'd REALLY like to see that come back as a Retro Track.
While later Mario Kart games had similarly themed levels, there's something about Toad's Turnpike that makes it special. Maybe it's just nostalgia, but I think it's a lot of different things. The music is fantastic, the level itself is simple, letting you focus on weaving between cars, and you gotta love it in Mirror Mode. One thing that I really dig though is that it feels like it takes place in the "real"/"our" world, and that's something that the later "big city" courses never captured.