I've worked for a few orgs where quality and testing were "everyone's" responsibility and it ultimately led to everyone pushing it off their plates and lots of it simply not getting done. Why? We could collectively borrow against the future and "everyone" being responsible meant that nobody could be held accountable, as then the debate would be in deciding fractions of responsibility.
It also encouraged those with other incentives, like product, to lean heavily on that to ship more features over doing reliable tech work as they figured the debt would be someone else's problem down the road.
People have this naive idea that people who are given responsibility will step up. There are those that do, but the rest often see the far easier path of externalizing problems and frankly most jobs reward that as they don't see externalities well.
I would have it so that platform team is responsible for identifying and engineering is responsible for fixing it. I am not sure that either team would have the skills needed to prevent such things from happening, so perhaps canary deployments would be the way to go if it is a substantial risk in your domain.