I think it's a good sign that Michael Bay has admitted this and hopefully this means that he will want to do a better job with DOTM. After all, the entire point of admitting to having made mistakes is to try to avoid repeating them. Well, he certainly won't have another writer's strike to blame for DOTM.

And yeah, as the director he would accept responsibility for the film's successes and failures -- if it's a problem with an actor or writer... whatever, you're the leader, therefore you accept responsibility. Such is the burden of leadership! (Rodimus Prime'd!!)