Is it as nice as Kiki's delivery service?
Well... I once watched Kiki's delivery service (I forgot the full Japanese title), it was quite a nice movie, though might be a little bit too long, it's thankful though we don't have to wait for the cooking scene in real time.
The same goes for Nausica (again, forgot the Japanese title), it was kinda nice, though plain too weird in some cases, especially with the biological weapons (who later on revived Nausica and healed her wound) and the weird enviroments.
I too also once watched Mirai no Shounen Boy (Future's boy, Conan), it was a nice series, though it later got too long. Conan meet Rana, COnan rescued Rana, Conan lived happily together with Rana in HyHarbor, it should end THERE! But oh no, Industria needs to be dragged again into the story and HyHarbor needs to be potrayed as thorny paradise. And not to mentioned it gone quite violent, I frankly have no disregard over the series again, especially after Rana gone violent on Conan, even if it's an effort to prevent Conan from getting hurt (a man/boy's ego is bigger than his body).
I think that I too also once watched Laputa (much again, forgot the Japanese title), as in, I seems to watched it, but I don't know if I really did watched Laputa or was it just a few clips of Laputa.
As for Howl's Moving Castle.
Yes, it's kinda strange that it's an old woman who is the main character, considering many others Studio Ghibli's works featured young people as the main characters. But hey, she was young to begin with.
For Howl's Moving Castle while being more romantic, it isn't way too romantic.
Actually, I think many of Studio Ghibli's works already potrayed many romantic scenes with even younger characters.
And a 13 years old teenager is actually already an adult, or at least a young adult. Even if one mean too romantic as in doing reproductive activity, since an adult is capable of reproduction, and girls aged much faster than boys. Though personally, romance, romantic stuff, and so on are just diversionary stuff that tend to lead people astray, making people lose focus of the real stuff, love.
Besides, with her being an old woman, I'm don't think that this is a case of being too young, it's a case of being TOO OLD. Another case of the obaa-chan (grandma) complex and oba-chan (aunty) complex if I can call it that way, in this case, obaa-chan complex.
An old man with a young girl seems normal, as long isn't he isn't in any competition with a young boy. An old woman with a young man, now... that's just strange, even stranger if a young girl is involved and was rejected.
Anyway. She did finally get her youth back, didn't she? Or did Howl became an old man? Then again, if Howl become an old man, it would be just like Shrek. Oh well, at least no species change. Or this is a weird man-woman relationship with a way older woman and a young man, and then just finished off with them stay the way they are or being separated.
As for Howl's Moving Caste being too slow and childish.
Hmmm... Maybe I will watch it in the future, sometimes when people said those things (too slow and childish), I find some things I like. Then again, I like The Phantom Menace, was feel so rushed with the same time dragged and in conflict with Attack of the Clones.
Unless of course that Howl's Moving Caste literally dragged the whole storyline and filled it so many weird things.