When gas stations and dealerships disappear, maintenance will be virtually impossible. My 2019 Jeep Grand Cherokee V8 HEMI is not a ‘shade tree mechanic’s” backyard project, and certainly not the muscle cars we worked on in the 60s & 70s.
I hear what you’re saying. It will be difficult. But it is do-able. Electronic parts will be problematic, but work-arounds and replacements will be found/made.
And I work on cars more than most, have OBD-II cables and computer software beyond basic emissions and fault checking.
Cottage industry repair will exist as long as it’s profitable.