Unreliable in the sense that they leave you stranded, or in the sense that you have to go to the shop for some annoyance?
My guess would be they globalized and are sourcing parts and labor from Eastern Europe and Asia.
My wife's Mercedes has 170k on the odo, and has been fairly reliable, but the catalytic converters going out at 130k was a major expense. Its replacement will most likely be another mercedes.
