If the system is built externally by vendor, you can change the vendor and it would create pressure on the vendor ecosystem to not create bad system. If it is

If the system is built externally by vendor, you can change the vendor and it would create pressure on the vendor ecosystem to not create bad system. If it is built internally you need people to be responsible to create reliable tests and someone to lead the project. In a way it's not very different than if your external system is bad or crashing. You need accountability in the team. Google can't fire "Google Ads" but doesn't mean they can't expect Google Ads to reliably give them money and people to be responsible for maintaining quality.