Wolf Children is pretty good but considerably worse then his earlier works (in particular The Girl who leaped through time) and really is not on the same level as Ghibli. I would say Summer Wars and Girl who leaped through time may compete with Ghibli Movies although they are also very different in style.
Don't agree with this at all. Wolf Children to me is his best film to date because as a complete work it shows his full maturity as a filmmaker who is able to concisely break down his ideas and themes into a well paced narrative driven by a consistent and focused tone. It has a very strong structure, and some of the best characters he has created in terms of being real people.
Summer Wars is probably his weakest film because it tries to do so much that it doesn't really have a strong grasp on what it's even about by the end of it. It's very similar to Kon's Paprika in that sense. A visual tour de force at times, but thematically weak overall. It's an exciting blockbuster with a good family spirit, but it pales in comparison with his previous film.
The reason why I think Wolf Children rises above even The Girl Who Leaped Through Time is because TGWLTT is a very emotional and passionate work which also loses a bit of focus towards the end. It's a very good film, but it has that indie film feeling where you can feel the personal passion of wanting to make something important, but it also has a lot of edginess and raw emotion to it that does give it unique character but feels it lacks a bit if experience to fully express itself. His One Piece film is also very similar - filled with very colorful unfiltered expressions of anger, done in a rather positive way, and I think a lot of those feelings actually resonated more with me there than in TGWLLT.
With Wolf Children though, there's less of that feeling, and more of a sense that a more experienced person is now carefully thinking about what he wants to say and how he wants to say it, and is able to express it well as a more mature storyteller. I lover that he tone has evolved to this level, and definitely hope it stays this way in his future movies because it shows substantial growth in his art form.