Vehicles under $15k are 1.6% of the market, and their share of the market has dropped over 90% since 2019. The old advice that you can get a beater and drive it in to the ground for $5k hasn’t been true for years but it still seems pervasive in personal finance spaces.
They definitely shouldn’t have flipped out at you about it, but that doesn’t mean they were wrong. Vehicles almost never appreciate in value; it just so happens that you accidentally timed the used car market perfectly.