Aegon is clearly much too cocky and thus set up for disaster, as you can tell from the last chapter. He may be portrayed as an amazing dude according to others, he probably really isn't. Remember how he practically fouled himself when they were attacked by the grayscale men on the boat. He may not even be a Targaryen.
'Half of the people that die return as zombies?' Only Catelyn and maybe UnGregor so far. Most people are actually dead.
Theon's semi-redemption was actually one of the best parts of A Dance With Dragons, and Joffrey's death has me laughing my ass off each time I read it. It' s a very inglorious end, which is exactly what he deserves.
When almost all the characters have their strengths, weaknesses, quirks, motivations, flaws... I really don't see how you can be calling them 'shallow'. How are people like Varys, Littlefinger and Melisandre 'shallow' when you can't even figure out what they want most of the time? I don't see how 'all the female characters are terrible'.' Catelyn, Cersei, Melisandre, Daenerys, Briënne all make an interesting read and they're definitely not simply male characters in the guise of women. Saying Arya (and by extension, Brienne as well if you're going down this path) doesn't count since she's 'a tom-boy' is ridiculous since her behaviour stems from a rebellious nature against what's expected of her in her misogynistic society (who says a girl can't act like her and still be a girl? That's only a conclusion based on cultural values), I suppose Briënne doesn't count either then? Maybe you simply have a problem with reading about strong female characters, as a lot of people (even fans of the series) seem to do?
Davos is an important character in books 2, 3 and 5, he may not be as prevalent as for instance Tyrion (who I've come to despise) but it's not like he's a minor character with hardly any 'screentime'. If you find a smuggler who suddenly decides to help out people and swears loyalty to the man who chopped his fingers off believable, I'm sure you can find a couple of other characters believable too. It also seems we're putting up the bar for what is considered to be believability for ASOIAF here, since I can name a lot of characters from a lot of series who are far less believable than any of GRRM's. Every nobody that somehow becomes the most powerful warrior / mage of his world in a few month's time ever, for instance, or every 'dark lord' that has no motivation for threatening the world other than simply because he can, and there's a lot of those.
You may think he's entangled himself, but so far, he's still making it work, and the way I see it it should be doable in 2 books, but who says he can't write 3 more? Whether he dies before finishing the series or not is not really meaningful to his abilities as a writer.
He does have his flaws, most notably taking the wrong decisions at times (the two battles that should have been the end and conclusion to ADWD were left out simply to provide a cliffhanger, which made the book incomplete) but he's by no means a 'shit writer'. A shit writer couldn't make a story of this scale work as long as it did.