Interesting; I feel it depends on the movie - they have a large portfolio now so some sort of averaging is inevitable.
I feel e.g. Cars franchise has limited vision. They're "allright", but not spectacular. I'm OK never seeing any of them again, even the first one.
On the other hand, I find Monsters Inc. a unique movie with a unique premise, and I can rewatch it regularly - with or without the kids 0:-). I also don't find it particularly sad. Inside out does indeed have a large dose of melancholy, but again I feel is a unique idea taken quite far without dilution.
(there are absolutely movies that are way more avant garde or quirky or surreal or even "creative" inasmuch as that can be objectively compared - but Pixar has two distinct audiences to cater to and they HAVE to be entertaining and attention-occupying to children; while inserting content that also keeps adults interested and even thoughtful - that's a specific set of constraints that e.g. "Love Death + Robots" does not have)
And if we look at their entire portfolio, the Pixar Shorts again have some absolutely brilliant, touching, "single idea executed to perfection" entries.