Haven't seen Sausage Party, but I'll say this:
If Sausage Party's claim to 'maturity' is that it builds itself up on sex jokes, then that doesn't make it 'mature.' If anything, that makes it juvenile.
If Sausage Party's claim to fame is that it uses the metaphor of food being stored to comment on religion, then regardless of whether you agree with your stance on it or not, then that does show a level of depth in its concept.
Similar to South Park: The Movie. On the surface it's swearing, and more swearing. Beneath it, it's a nice set-up on the nature of censorship and communal 'outrage culture.' Or, Zootopia. I've argued that if we cut out the themes within the movie, it would still be a good movie, because the plot, action, and characters are executed well enough. Its use of themes is what elevates it to a great movie. Likewise, I can respect The Angry Birds Movie for conveying its own anti-imigration, anti-multiculturalism message, even if I don't agree with it. What I can't stand is that it's absolutely obnoxious to watch. Angry Birds isn't 'mature' just because it falls on the opposite end of the socio-political spectrum as Zootopia, it's juvenile because of its manner of delivery.
So, there lies the rub. 'Themes' in of itself doesn't make you mature. 'Edginess' doesn't make you mature by itself either. So when we talk about 'maturity' in animation, my main question is "can I, as an adult, enjoy this?" Angry Birds aside, most of the animated films I've seen this year have been "yes." Shouldn't need to explain Zootopia. The Peanuts Movie is a charming movie that encapsulates the trials of growing up, and conveys them in a respectful way that I, as an adult, can appreciate. Finding Dory is a delightful film that has likable characters, a good story, and while not a deep insight into the nature of disability and how family/friends deal with it (or fail to), is an insight nonetheless, and certainly a sign of maturity. Even Kung Fu Panda 3, while not a deep film by any means, still at least had some level of depth to it (often said that KFP1 isn't a deep film, but does have depth in it), and while grating at times, still had an overall theme, not to mention that the animation was absolutely gorgeous. All of these films have (elements of) maturity in my eyes, all of them are accessible to children. A film doesn't need to be 'adults only' to be mature. So I may see Sausage Party, may not, but it's only in the knowledge of reading reviews that it does go beyond the obvious sex jokes that I'm considering it.
To comment on some other examples:
-Family Guy: Garbage. Maybe it was good once, but now, I just can't stand it.
-The Second Renaissance: It's mature, but the use of blood and gore isn't what makes it mature. It's mature because of its subject matter, and how it approaches said subject matter (e.g. the use of an abstract protagonist - humanity itself).
-Simpsons: Well, at least classic Simpsons is the definition of "for all ages." A child is going to love it for the character dynamic and humour. An adult is going to love it for those reasons, and for its clever sattire and examination of Western/American culture, faith, politics, etc.
-Rocko's Modern Life: Loved this as a kid, haven't seen it as an adult. But I feel it proves my point. As a kid, I loved it. If I can enjoy it as an adult, then it only elevates the cartoon further in my eyes (and I'm aware of RML having some stuff that you wouldn't believe got past censors, such as when Mrs Bighead tries to seduce Rocko).
-Captain America: Civil War: Why does everyone keep mentioning the airport scene? I always thought the best fight scene as at the end, when Tony and Steve fight, because there's actual emotional investment/conflict. The airport scene is more "let's get these heroes to fight for ten minutes because the plot says so."