This has been an informative thread. I agree with the OP in that anything with wheels is a depreciating asset, ESPECIALLY in today's market of overpriced stuff that is almost impossible to work on by oneself.......it's as if it's by design
But, back to topic.
I haven't relied on a mechanic, other than myself, for as long as I've been driving. The ability to do my own maintenance and repairs has saved SO much money over the years. I feel doing my own maintenance gives me the ability to have eyes on my vehicles at a more consistent interval. This prevents surprises from popping up more often than not.
There are caveats though: location is one, previous owner maintenance, etc.
If you live in a rust free area, this makes the whole running it until the wheels fall off way more practical. Rust belt requires much more focused care and prevention that will still add to longevity, but can be a PITA.
Previous owners can be a blessing or a curse......I've had both over the years. Sometimes the best intentions can still come up short, which then makes the used car case more expensive, prohibitive sometimes, or can completely cure someone of wanting to deal with it.
I've found that FOR SALE BY OWNER is the best route to gage what you are getting. And, buying from a rust free area is worth its weight in gold.