If you check out the other ISPs at ProductReview you certainly will see many complaints but unlikely as many as Optus. I was absolutely astounded at the huge number of complaints in the worst category. I think it unlikely you would find anything as bad as what happened to us: being disconnected for 3 months because of Optus negligence and then the company playing the blame game as well as refusing to fix the problem.
You are correct about the ACCC. This organisation has no interest in doing the job it was set up for and normally undertakes one investigation a year to justify its existence. If you ever contact the ACCC you'll get correspondence from it suggesting you fix the problem and be fobbed off to somebody else who also refuses to act against dishonest businesses.
The Australian public has certainly been abandoned and this extends also to the ASIC. Big business has become all but unaccountable and has now reached into governments. That leaves consumers there to be milked and abused.