You really need to read the entire article, there's a lot of context missing from the paragraphs I pulled out and he covers a lot of the issues you brought up.
DC's restrictive policies regarding its tentpole titles isn't the issue here, it's the fact that there appears to be an undeniable pattern of inconsistency, underhandedness and at times plain incompetence in the handling of creators, which has resulted in the exodus of disgruntled talent that we've seen over the past few years. A lot of people have a lot of bad things to say about how DC is being run right now and at no point does he didn't imply that this centred around the ringfencing of DC's top tier characters, so not sure what you're getting at there.
Wonder Woman is very much the exception that proves the rule in this instance and as a result her solo book is completely incongruous with what she's supposed to be to the rest of the DCU. The Wonder Woman in Trinity War is nothing like the one that Azzarello is writing.
Funny you should say that he elaborates further on Dial H. Karen Berger, the very same person that championed it, has now left DC and was critical of the direction the company is headed in.
I'm not seeing the contradiction you're hinting at. Dial H is only one book, its existence does not change the fact that the vast majority of DC's books fall under extremely heavy handed editorial mandates and surely the fact that it could not be incorporated into DC's inflexible mainstream proves his point.
No, I think you've misinterpreted what he's getting at there. He's not saying they shouldn't exist in the same comics he's lamenting the fact that DC felt it was necessary to streamline the characters in order to put them in the same crossover. Constantine in Hellblazer was dark, sophisticated and uncompromising, now its sarcastic one liners, cynical exposition and pissing contests. Pre Nu52 Shazam allegorically defined how childlike idealism and purity is the prism through which we interpret the ethics of superhero comics (it doesn't have to be one or the other, now it's sarcastic one liners, cynical exposition and pissing contests.
And please be real, the Shazam story was a backup in one of DC's most popular titles and was written by one of the primary architects of the Nu52. The characterisation and tone in that is clearly what they're going to use going forward, you can't just say "it doesn't count" because it doesn't have a cover.
Was nobody else confused by the fact that this event that they'd hyped up since the very first issue of every single book and built up as a game changer turned out to be just a tepid preamble to a crime syndicate story?