PE exists because the cases you hear about are the failures. It would be like looking at the products of Google that never made money and then wondering how Google runs, you're not looking at the full picture. For every failure story like this, there are numerous other firms where PE has come up, removed a bunch of inefficiencies, driven up profits, and then moved on. It is just a more involved form of VC investing, and in that world failures are even more common.
Sure, PE is bigger than this. But isn’t the issue people are having is that this “failure” isn’t a failure (PE gains something)…it’s part of doing business as a PE firm?