This happened to our DC2, but nearly thirty years ago so I don't know whether the treatment he had would be considered appropriate now. On his second visit to the dentist, we were told that practically every tooth needed filling. For several reasons, we moved the children from that dentist to mine, who had a much gentler approach to children. He confirmed that DC2's teeth were bad but recommended 4-monthly fluoride treatment to try to prevent further decay, and going on to a sugar-free diet. He said he wouldn't want to extract or fill any teeth unless really necessary, e.g. if DC2 got toothache, because that could put him off dentists for life.
All that worked very well, and no extractions or fillings were necessary. The fluoride treatment continued long after his adult teeth came in. The going sugar-free was a bit difficult to begin with but we used recipes in a book written by another dentist which used only fruit as a sweetener in puddings, cakes and biscuits. It did take a while to adjust to the lower level of sweetness, and we weren't completely ruthless ? both DCs had school dinners so they had puddings the same as everyone else - but we didn't allow sweets or fruit drinks. As neither DH nor I used sugar in tea or coffee, we were only buying a bag of sugar roughly once a year, and then it was only used by visitors.
I don't know whether that kind of hands-off approach would be acceptable these days. The only downside to that conservative approach was that DC2 did have bouts of bad breath until his baby teeth had all fallen out, which may be a good reason for a more active treatment plan.
I wonder if some dentistry people could comment as to whether that approach would be appropriate these days or maybe, if it would, whether the NHS fee structure in dentistry would make it difficult for dentists to offer that approach on the NHS (we paid for the fluoride treatment privately).
But I do understand the guilt thing. Oh yes, I really do.