That is a good thing if you care in the least about security. Being secure is a selling point of browsers, and hence they take code quality seriously-- bug trac

That is a good thing if you care in the least about security. Being secure is a selling point of browsers, and hence they take code quality seriously-- bug trackers, bug bounties, regular and automatic updates. History has shown that third party plugin providers care not even a little bit about how slow or broken their plugins are, because they have a monopoly on that content you want to view. As a result, in a world where the content creators control the plugin code, everyone ends up with broken, insecure, slow plugins. We're trying to exit that world. Don't start getting nostalgic for it.