COOL / HAND / LUKE, one of the classics! Pete gives us the (oft-misquoted) WHAT WE HAVE / HERE IS (a) FAILURE TO / COMMUNICATE. Imagine how much it would stink if you were that actor, having delivered an incredible line … only to have people say that you said it wrong?

Both work, grammatically. There's a good case for the line as is since that implies multiple instances. Given Paul Newman's constant needling of authority in the movie, that's clearly the case. So why do so many people insert the "a"?
I DON'T KNOW, BUT WE JUST DO.
Theme felt thin, what with just the movie title and a single quote. But the quote does take up a good amount of real estate: 11 + 15 + 11 = a lot of squares. And when you consider how difficult splitting up COOL / HAND / LUKE makes things, I can see why Pete didn't try for anything else.
Wait, wait, wait, failure to communicate, you say! What's the big deal about putting in three little teeny tiny itsy bitsy words? Well, let me tell you! Check out that south section, bounded by COMMUNICATE and HAND. Fixing a ceiling and a floor into a region like this is akin to eating 50 hard-boiled eggs. (I love that scene, Pete!)
It is true that Pete could have shifted HAND over one space to the right, so that did give him a little flexibility. But not a lot. So, not a surprise to get a rough crossing in MITA / OTOE in that region. This isn't a friendly crossing for novice solvers. Perhaps on the order of eating ten hard-boiled eggs.
Along with some USE NO, ETE, OF IT, and the dread OSO (O SO unfriendly to newbies), it's too much for a Monday puzzle. I did appreciate Pete's efforts to work in some extras, though — I CALLED IT, OLD FLAMES, and LETS SLIDE. Important, given how thin the theme felt. So tough to find the right balance.
I enjoyed the shout-out to one of the greatest movies of all time. I would have loved something more, though. Hmm … hard boiled eggs look like Os…