Electrical problems subaru outback 2005

First the back-up lights went out, then dome light then AM radio. Mechanic found several eletrical wires in trunk cover harness broken due to frequent opening and closing of hatch cover> (Bad engineering or something else?)

Electrical problems are a rarity with Subaru brand. You probably got either a badly installed from factory wiring harness or maybe some body work does along the way if used and improper reinstallation.

Was this car purchased as a used car?
If it was, then God only knows what the car may have been subjected to prior to your ownership of it.

The wiring harness should not be damaged by frequent opening and closing of a door, trunk lid, or hatch. Something is fishy here.

Did the lights stop working because of blown fuses? Does the FM radio still work?

This car was bought new!

It should not, but it certainly happens. Same with the wires going to doors.