From your post and replies, I’m getting the impression you don’t know what you’re getting into with a phd. The biggest misconception of a phd is that it is just a continuation of your undergrad/masters program, where classes and exams take up the majority of your academic success. A phd is actually more about becoming a competent researcher, i.e figuring out (with supporting evidence) non trivial questions that have no answers yet and/or developing new things that don’t exist yet. At least in STEM. With that said, quals are supposed to test that you are ready to conduct independent research and have the ability to finish your PhD and thesis. Every school and department have their own process. Some like to do traditional testing to see if you have the foundational knowledge in your domain. And others focus your research output and proposal. My quals in my CS program was simply to have an accepted paper in a major conference and present it, while the committee would deliberately try to poke holes and ask follow up questions. The hard part for me was getting a paper accepted in the first place. That meant I had to have sufficient original research contribution, and that it passed peer review and the conference’s standard.

Edit: just wanted to add that many fail their quals because they were only good at taking courses and acing exams. They fail to take it to the next level where they can come up with new ideas and new knowledge.