Fluoride toothpaste was not introduced in the U.K. until the 1970s and made a massive difference in rates of decay .
The whole reason the vast majority of people needed so much treatment in the 60s and 70s was because amount of sugar eaten daily was higher , there was no fluoride toothpaste and dental materials meant any intervention had to be a bit earlier than now eg there were no fissure sealants or fluoride varnishes etc .
Decay rates and fillings dropped massively in the U.K. during WW2 and during rationing because the amount of sugar containing foods was so limited . It then started to rise in the 50s as sugar came off rationing and as we came into the 60s and 70s when rates of sugar consumption rocketed.
There is no way a dentist looking after treatment , unless they can see x rays and photos of teeth , can say whether or not a filling was needed . Particularly as once people are past childhood and teenage years their diet and cleaning habits normally get better.
The philosophy around taking wisdom teeth has also changed over the years , although most dentists would say , on the NHS, the pendulum has swung too far the other way and more wisdom teeth should be taken out earlier.
Im sorry to say over 90% of all dental treatment is preventable . Keep the sugar attacks to three times a day (the majority of U.K. children eat more than 7 times a day and both adults and children eat many times the daily recommended amount of sugar) . Stop smoking, keep diabetes under good control and learn how to clean effectively .
I am over the age of OP and have all my own teeth other than those removed for braces and one I cracked. I have had no fillings for 40 years . My partner had had many fillings and gum problems until I met them and they amended their diet and cleaning and stopped smoking. Come lockdown they, alongside a lot of the U.K., worked from home and picked up bad snacking habits , cue more dental treatment, the first time in many years . They have now got back on the straight and narrow and no more treatment. Both their parents had lost their teeth by their age. They did not inheirit bad teeth and gums , they inheirited bad diet and cleaning habits and smoked.