Pushed back, but for absurd reasons (The Flash). Let's be honest here... they were pushed back because they decided to shift directions entirely.
But before even that, Flash had trouble keeping a director, it wasn't until the 2nd one (who signed on and was even talking about it) dropped out that they decided to completely do a page one rewrite. They signed him and then came to the conclusion there were creative differences months later.
I can't be the only one thinking it's real foolish for them to be dropping these films without building up their core Justice League members. There should be a sense or reason for these...now that SS has dropped, was there a reason why it was released in that time frame? Their focus should be on the Trinity, then the League, then these side characters.
And no, it wasn't the Rock that was the breaking point (he's probably not even in this if the rumors are true, even dumber...). I would've had the same reaction if SS2 or Gotham City Sirens hit first too.