I never thought of this movie as carnivalesque, but you could argue about that. I like to think it is surrealistic in the way that your memory can distort history and all that you once dreamed of or was scared of. Those memories evolve into caricatures of persons, their behaviour and caricatures of situations. We not only see Federico's memories, but also the supposed memories of people once surrounding him.
Also this is said to be Fellini's most accessible film. Well, I was 15 when I saw it first, and it is still one of my favorites. About 10 Fellini-films later I read that this won the academy-award for best foreign picture, which I never expected, but think is quite rightly. The many surrealistic scenes stick to the mind for decades. Hilarious, tragic, oppressive (upcoming fascism: so most of it must take place just before ww2), nostalgic, poetic: there's something for everyone (and every age) to appeal to, while Fellini makes no compromises. If this was higher-paced, you wouldn't have time to appreciate the details, the photography and the music (Nino Rota). Don't look for a plot here.
The cinematography (Giuseppe Rotunno) has comparable feel with some films by Mike Nichols (Catch-22 (1970), Carnal Knowledge (1971), Graduate (1967)). Rotunno worked with Mike Nichols on three films: Carnal Knowledge, Regarding Henry and Wolf. And with Fellini on 9 films (e.g. City of women (1980)). I don't know if this is relevant, but Fellini is said to have had a conversation with Mike Nichols during the production of Catch-22. Otherwise I can't think of many films that are comparable with this fabulous collage of events happening apparently in spring, summer, autumn, winter and ends in spring to conclude some cycle (generation ?) accompanied by beautiful distinctive music. Why o why can't we vote 11 :(
