How do you define reliable? Most cars will be reliable if constantly maintained and repaired to a high standard. Many car owners do not check every component regularly and rely on a service and the MOT test fail or advisory notifications to do that once a year. Is reliability measured by how many items fail and need replacing? Every car I have owned, cheap or expensive, has had a few things that have become known as common faults for that particular vehicle.
Some people may view reliability as how long things keep working without needing repair or maintenance. Some cars may be made to a price point, and specify cheaper components to achieve that. Some cars may be made for a "luxury" market at a higher price and may use components that cost more but also last longer without fault.
I have two rusty fog lights in my fiat, 13 years old. I have two clean fog lights in my Volvo, 21 years old. The difference is either in design, where one is designed to be better protected from corrosion, or in the quality of components used which may be determined by cost.
