It was never worth what he paid for it, and his "enlightened" changes have only made things worse in terms of value.
One big thing that must be bad for advertisers is that generally, even people without a Twitter account (I've never had one) generally needed to view posts from some businesses or services. So they still had people coming by and serving ads to them without an account.
But now that you cannot even see comments on a tweet and if you're somehow able to get to a list of tweets (it usually just forces you to the login screen) you cannot get ANY useful order from it when not logged in.
Believe it or not, I think the majority of people won't create an account with a gun to their head like this. As such, the advert revenue is already down from people like me.
Furthermore, though, I suspect businesses will eventually work out that Twitter is no longer a suitable bullhorn to use to deliver promotion information or to offer customer service, and will start to move away. That's not going to help Twitter or their advertisers out either.
But, I don't think he ever planned to make it profitable. I think this weird anarchy he's iteratively implementing was what he decided to do, as soon as he was forced to finish the acquisition.