At some point, you have to make the determination as to who and/or what you're going to trust. Testimonials can be impactful to a certain extent. Virtually every RV related comment on this website is a form of a testimonial. Amazon has a zillion of them (many of which are very fake). And our health co-op provides them too. Based on my personal experiences with this co-op and the overriding faith-base that I subscribe to, I choose to believe that the program is truly effective. I've honestly seen more people get run through the ringer with their traditional insurance plan than I can even remember. Some of that is due to a lack of understanding of the policy parameters, but some is just because insurance companies can be an absolute pain to deal with. An "english-challenged" phone screener in Inida is a not what I want to hear when I have to make a call regarding my insurance policy.
FWIW, in this day and age, I don't think thre's any significant risk involved in choosing a health cost sharing co-op. If I learned that I had cancer and needed treatment, if there was any inclination I had that my co-op might give me trouble, I could switch to traditional insurance and not miss a beat. Even if there was a minor waiting period prior to coverage, I could figure out how to minimize cost during the wait (hopefully). Everything is a hypothetical. Even if I had traditional insurance, there's no guarantee they would provide coverage for the particular specialist that I may need at that given moment.
Really, though, much of this boils down to the availability of a competitive insurance market. There are only 2 health insurance companies available to me in my market. Note that I could choose from literally hundreds of insurers for auto, home, liability, etc. But United and BCBS are my only options. BCBS wouldn't write a policy for my company. So I'm stuck with United. Fortunately, they've been good to work with, but I can only imagine how costs might be more competitive if I could choose from more than 2 companies.
At the end of the day, making the choice to use a faith-based health cost sharing co-op is heavily philosophical in nature. For those who don't share the same beliefs, that concept may not make as much sense. Topics and discussion of religion are prohibited on this forum, but there is a Bible verse which explains exactly what I'm talking about that I'd be happy to share with any member via the PM function.