As many have commented, compared to the best Ghibli works, it can't measure up, but considering this is the first movie of the new studio, they did amazingly well and it could easily be one the mid-tier Ghibli films.
The movie is great on a technical level and even the worst aspects are perfectly servicable. They've got the craft down, now they just need to find a compelling vision to bring to life with it.
All in all I liked it a lot, my nieces loved it, and if the team at Ponoc manages to gain some momentum we've got great things to look forward to.