Yeah, he's definitely not a new author. He's relatively young, but he has seven quite good adult fantasy books under his belt outside of WoT, each of which I personally like better than the Wheel of Time series, but for different reasons (they're different types of stories, and WoT will always have an important place for me).

A better excuse is probably that he's working in someone else's world, dealing with astonishingly high fan expectations and a fan base a dozen times more interested in nitpicking the details of the books (as they did with all of Jordan's as well) than his own fan base, working with an editor (Harriet) who is more personally invested in the story than any other editor he's worked with, probably secretly wanting to get through it so he can return to his own work, and essentially being asked to write fan fiction from notes. There are quite a few things he could have done differently, but there are quite a few things I think he did well, too. I for one have really enjoyed Egwene's arc, Jesus al'Thor, the forging of Perrin's hammer, and even Mat's humour. The little details aren't what they used to be, but I'm enjoying getting a faster-paced end to the series.

P.S. It's actually considered generally poor writing to put adverbs to the way people say things, ie., "Moiraine said coolly" or "Moiraine said acidly" the way you're describing. I don't remember if Jordan actually did it that way, but it's considered generally better to simply use "said" by itself and to let the dialogue or the contextual narration convey the tone. But as with anything, tastes and styles vary.