Put a list of Ursula Le Guin works on a wall and throw a dart at one of them. Don't know which one you threw a dart at? That's okay, because absolutely none of them have gotten good adaptations.
The only exception, extremely ironically given I'm saying this, is Tales of Earthsea. The first half is alright but I guess they lost their train of thought during the second act (their words not mine) and it became a Legend of Zelda story. Still not terrible though, I can't understand why people hate on it when the same people love Ponyo.
What Ghibli films don't have plots? Ponyo, Totoro, Arrietty, Poppy Hill and Marnie have plots. Whisper of the Heart? I don't remember the plot of that one.
Tales From Earthsea's problem was the predictability. The course of the story was formulaic. Ooh there's this evil wizard who must be defeated, big deal. Ghibli characters are usually more complex. Villains should have something noble or beautiful about them to get some of the viewer's sympathy. When the protagonist was imprisoned and then the friend came and saved him, it was just too predictable. The rescue could have been done artfully but it was not.
The villain of Castle in the Sky was similarly boring, but the colorful supporting cast made up for it.
By a plot, I mean a structural one. None of the ones you mentioned except for the last two had plots. The studio is famous for going on record saying they go out of their way to make their movies scriptless, instead preferring pure improv, though it kind of shows in how freeform and non-rule-based it feels. To be fair though, it does help to have read the book it was based on, you get the context of where exactly the movie begins to lose its identity (and appreciate it was trying to have one).