With new cars requiring more complicated parts they are getting more and more of a simple monopoly on work removing our ability to choose who we want to do the work.
Agreed! And I think this entirely purposeful on the dealer's part.
I think modern auto-repairs are a huge rip-off scheme (by dealers) that's largely gone unreported.
If you're NOT lucky enough to be married to an auto mechanic these days, I can only suggest, well, come to think of it, more than one thing:
1) Get a pre-1990 car, which can be repaired by your local independent shop. (Our cars are 1986 and 1980.)
2) Pester your dealer for a diagnosis, using their equipment, and do your best to pass this information on to your local independent shop. (Write it all down!)
3) Talk directly with the mechanic, who's doing the work (your dealer will try very hard to prevent this), and ask what is really wrong with your car. Beg him/her to only fix what really needs to be fixed.
4) Get a horse & buggy instead.