Even if your car is from the same brand as the dealership, they may not be equipped to service it. At what point does that become reasonable? Just how old is too old?
For example, Mazda rotaries are infamous for being unservicable at Mazda dealerships, even when the RX-8 was barely a decade old.
the alfa dealerships are notorious for this, anything prior to the rinascimento they do not touch.
which i find is unreasonable from such a storied brand banking on their history, they need a classic program like porsche or mercedes, who are good to classic cars.