... but suing over the semantics of a piece of paper to somehow ignore the implication that a diver was, in fact, responsible for their own death is symptomatic of the fact that in this day and age, nobody is prepared to accept their own repsonsibility for anything.
No one was suing over the semantics of a piece of paper. The family of the deceased was suing over his death.
Ordinarily, it would be for a jury to decide whether the dive shop did something wrong and whether that thing was a substantial factor in the diver's death. In making this decision, the jury has to evaluate the evidence and resolve conflicts in the evidence to find the facts. However, sometimes, there is not a dispute over the essential facts. When that happens, there is no need for the jury to find the facts as they are already there. When there is no dispute over the facts, the judge can just apply those to the rules of law and make a decision.
The procedure for asking the judge to apply the law to a set of undisputed facts is called a "summary judgment." The basic idea is that the moving party, whether a plaintiff or a defendant, submits a set of "facts" to the judge. Each "fact" must to accompanied by evidence that, if believed, would prove the fact. The moving party then identifies the applicable principles of law and argues how the "facts" when applied to these principles, compels a ruling in its favor.
In the Catalina Scuba Luv case, the dive shop essentially submitted a set of facts showing the waiver. From this, it attempted to show that applying the law to the facts, it would win, regardless of whether it was negligent or not.
In the appeal, the court basically said that the waiver was not effective and did not compel the conclusion the shop was not liable, regardless of whether the shop was negligent or not.
So, basically, the deceased diver's family sued; the dive shop presented the waiver and the Court of Appeals said that the shop could not get out of the lawsuit based on the waiver. It implicitly said that the deceased diver's family would have to show she shop was negligent and that the shop would have to show it wasn't negligent.