This is not correct. Many cameras have "simple" mechanisms because of cost-cutting concerns, and they will not necessarily be more reliable. Many times you can make a more reliable mechanism by ADDING more parts such as ball bearing races on rotating axis, etc. A camera like a Canon F-1 has many many more parts than a machine like the Nikon EM, the F-1 is much more reliable not just because of better materials, but also because it has more mechanical components like bushings and bearings to reduce friction and thus wear and thus add reliablitty.
A camera like the Exa has a shutter that is extremely simple in parts, yet it isn't the ultimate reliable machine and the precision of speeds is questionable due to the simplicity of the mechanism itself.
No, this only tells you the camera is easy to diagnose - it has nothing to do with reliablity. Again, Exa.
Electronic components in most cameras are very very reliable. It's the electric parts that require cleaning or resoldering. Just as mechanical parts require cleaning and relubing.
Yet the big elephant in the room is that mechanical components can fail with no replacement available. You would need to have a shop machine the part, and some times the shop can't do it with a material, precision and quality of finish that would make for a reliable replacement. This was under discussion lately on a camera repairmen forum.
Broken pits in ribbons -- which often are caused by a bad technician, can be overcome by jumping with wires.