Nice analysis. I've followed the same path as you. I decided that the 2002 and 2003 Volkswagen TDIs with the ALH (million-mile) engine was the one to own. Simple engine and fuel injection system, manual transmission, minimal emissions equipment, abundant after-market parts availability. Excellent fuel mileage. Corrosion is a problem but not as bad as pre-1999 ones.Path 2: You buy and hold an older car (or cars) that you can fix.
Like I mentioned above, I think my plan is to assemble a family fleet of vehicles that were in very common use (or use parts-bin parts) in their day, but are from the late 90s or 00s. Things like Pather body Fords, Full Size trucks from the big 3, etc will have parts available for decades and decades because of the sheer volume of production, minimal changes over long life-cycles, and size of the aftermarket. With this approach, when you need a car you go out and you buy the nicest, cleanest, lowest mileage example of an older car that you can afford, and you maintain it with the goal being to keep it as long as you possibly can.
I honestly think that in the next 20 years there is going to be a huge run on the market for 90s/00s cars because I know I'm not the only one who considers them the "sweet spot" in terms of safety, tech, comfort, etc. Just new enough for airbags and fuel injection, just old enough not to have the insane level of tech. I personally would rather start buying up the cars I want from this vintage now while they're cheap and plentiful than wait until their values start climbing and availability tanks.
I've got two for my own use (a Golf bought new in 2003, the other a low-mile '03 Golf in 2014), one for my sister and her family (an '03 Jetta wagon bought in 2018), and recently a nephew picked up a nice '03 Jetta. Lately I've noticed that rust-free well-maintained TDIs from that era are slowly rising in value, even as more of them exceed 300k miles.
Edit: you can still find excellent rust-free well-maintained examples for $3000-$5000 if you wait for the right one to come along, and you insist on one with a manual transmission (the automatics suck). Take care of them and they may serve you well for another couple of decades.