Well, at no point was the qualifier "recently" in the OP. It was a blanket statement brooking no qualifiers. As such it doesn't hold up.
If people think that Dini RECENTLY has been poor, that's another matter.
I never read Countdown because the concept didn't appeal, though I think it's fair to say editorial had a hand in the end product (Little things like switching out go-to guy Dick Grayson for run-from guy Jason Todd at short notice can't have helped) nor Madame Mirage, though I heard good things about it.
To summarise a few of my own thoughts though; Dini's Alfred has been excellent throughout his Batverse run, as have his civilian personalities of the Batclan.
He hasn't written Bullock much that I'm aware of. His new status quo for Edward Nigma has been inspired (and much better than the Hush/post-Hush what-were-they-thinking Riddler).
His corrupt business Penguin has been fine, his Zatanna a great deal of fun interacting with Batman.
He even managed to make Hush himself, a TRULY awful creation, actually interesting and a semi viable threat. His Bruce Selina interactions were fantastic.
So no, even with the "recent" qualifier, I can't agree with the statement that Dini's writing of characters has been bland.