The over-arching theme to the movie is that the joker is creating chaos to push everybody over the edge and reveal their baser, corruptible side, which he is convinced everybody has. Perhaps you can read into his drive a desire to vindicate his own 'craziness'. If you analyze closely enough, perhaps you can dig up some illogical scenes but I won't label them plot holes (which I consider to be obvious gaffes). To me, the director provided enough throughout the movie to earn
a suspension of disbelief and hence I enjoyed the movie. Unlike Indy 4 which was ridiculous.
While I understand that you did not like the movie, your opening statement 'if this is the best Hollywood has to offer ....' is a bit over the top to me. That is the statement which caused me to question your post. If you are looking for entertainment, you can do far far worse at the movies before proclaiming that Hollywood needs to start from scratch.