What's wrong with The Goldfinch?

Let's look a little more closely as some of the problems that beset Donna Tartt's puzzling novel The Goldfinch. I went back and re-read the crucial (seemingly) section in which narrator Theo wakes up after the terrorist bombing in the Met museum and has a long colloquy with the elderly gentleman whom he'd been watching - actually, watching the attractive young woman with him - as they'd walked through the galleries. Looking back on this section, the old man goes on for literally pages of babble - some of which we learn much later refers to various people in his life - the key point though is that, first, he tells Theo to take the eponymous Goldfinch painting and, second, he hands him a ring and tells him to bring it to Hobart and (something?). Looking back on this scene from about 250 pages farther along, it's pretty clear that most of it is pure drivel - it doesn't matter a bit for the plot, and it adds nothing, no insight, no color, no mood, nothing - just words. Worse: Theo leaves the building, goes home - and then we follow him as he narrates months of his life, his sadness at school, his tenuous relationship with the wealthy family that has taken him in - and then, boom, all of a sudden, he looks up Hobart & something in the phone book -white pages no less! do they still exist? - and goes to return the ring. Is there any way that this is likely or credible? A more efficient writer would have the old man say : here, take the painting, and bring it to Hobart ... and that would be Theo's mission once he was safe. Now look readers of this blog know that I am not a philistine, I don't think everything has to be about plot, and in fact I don't even read or enjoy mystery novels. I asked for volume 3 of Search for Lost Time for xmas for god's sake. But this novel is just slowly grinding away, without moving the plot forward in any engaging manner - and without the compensating virtue of a rich, atmospheric setting, style, insights, or observations - just very generic depictions of a a certain NY social set. And when Theo meets the furniture-restorer, Hobart - H. tells his life story in pages and pages of so-called dialogue. Writing 101: show don't tell. Not here, though. So what's happened to Tartt? She can be so damn good, and some sentences still show that - though they don't at all sound like a 13-year-old boy nor like a 27-year-old man recollecting his boyhood. She's so out of touch - to give just one example - the family Theo's staying with doesn't want him to be bombarded with news about the bombing, so they keep the NY Times away from him. Are you kidding? That's where a 13-year-old will get the news? I could go on - and I will go on reading this book because somehow I do have faith that Tartt can do better and that she will pull this off, but I'm on shaky ground here.