Mike, are you speaking for yourself; when you make major purchase decisions you have difficulty thinking for yourself and fall back on trite mantras? Or do you believe the rest of us are lacking critical thinking skills and thus need mantras to make decisions? I'll guess your going to claim that your comment isn't directed at yourself or others, instead it's a guess as to motivation of nobody in particular for such activity!
To the OP, in 30 years I've purchased 5 new vehicles and 2 vehicles which were not more than 3-years old with (1st one) 30k and (2nd one) 17k miles. The used vehicles were both Toyota Camrys. The 1st purchase was significant savings off new price, I know what I paid but don't recall what new prices were back then. So to avoid challenges to my veracity I'll just leave as it was worth it to me. It was private party sale and I negotiated 20% off the original asking price. The 2nd deal was fair but not a significant win like the first one was; this was via a Honda dealer who took the Toyota as a trade-in. These transactions were 10 years apart.
My next Toyota I expect to get new, if I buy Toyota. But, I'm thinking of a luxury car and will probably look for 2-3 year old and compare it to new before making my decision. I won't rely on any mantras, in fact I don't know what the mantra is for the luxury make I'm considering.
I can afford any mass produced new car I want, but I consider each purchase decision separately. I did learn about "buying used" back when it was a larger discount for certain makes & models. With the ubiquitous leased cars on the market along with rental cars resales and the ongoing transition from sedans to crossovers it seems like there are great discounts for some and for others buying new is better. When I buy new I like to find a prior year leftover early in the new year. I have additional strategies I learned from a friend in the business to improve the chance I'll get a more eager sales manager.