Being a former farmer, I can tell you that in general if you're buying new farm machinery you're doing it wrong. The basics of most of the stuff you would need a tractor to do (or almost any farm implement) has been the same since the 50's or so, and tractors tend not to have forced obsolescence as much as, say, passenger cars do. I can pretty effectively repair a John Deere or Case up to, say, 1980's, and there's no shortage of those out there since many small farmers (the kind most likely to hold onto old gear) have gone out of business.
I don't know if the current paradigm is really all that different from several old ones. Companies used to switch up parts specifically to make it so it wasn't worth it for most people to manufacture replacement parts on their own, and would often only sell certain pieces of the suspension, etc, as large groups of parts, not individually. The manufacturer always has found a way to get a piece of the local garage's pie, and all that's happening is that they're changing what the piece is. Also, how does a good mechanic learn? By taking things apart. Once a few of these new cars hit the junkyard, your local mechanic will know how to fix them. Possibly even before, since beyond the onboard computer itself most things stay about the same.