Given that SOPs are really only 'SOPs' when they are written down I see precious few folk who have the benefit of their support.
Been flying for 45 years, mostly FW and more recently RW, but never for pay. Reading accident reports has made me a true believer in SOP's and in the quote above. Have developed what I call a Personal Safety Management System tailored to the owner/pilot. Did quite a bit or research on SMS's and found that virtually all are aimed at organizations consisting of tens to thousands of people and multiple layers of management. I wanted something for an orgization consisting of one person. My PSMS includes a Flight Operations Manual which incorporates SOP's, together with an integrated set of checklists, briefing scripts, and other info/documents. The core of the checklists is based on the RFM (B407) but with additions to enhance safety based on experience and expert advice from "pro's" who have reviewed the PSMS. I believe that this kind of discipline greatly enhances safety and contributes to the development of a safety "mindset" (sometimes called a "safety culture" in organizations of more than one person). Some will chafe at the discipline that this imposes, but I have a personal style that likes discipline. My insurance underwriters have reviewed this system and have made very favorable comments. The PSMS is a work in progress and is updated at least annually to incorporate new information and to improve usefulness.
I am in violent agreement with those who disagree with the "wing it" approach. Aviation seems to attract a disproportionate number of those who "know better" and I have met my share over the years.