Google knows load performance is a critical user need from the ample data they collect from Google search users, they've talked about this before. I forget the exact number, but every 100ms less load time drives significantly more traffic and engagement. I have no idea what data you're looking at that implies 5s load times are not a problem. I, for one, am overjoyed the Google is tackling this problem and succeeding at it.
Google has applied performance penalties to sites before and it still does. It's not enough, and there are limits to the penalties they can apply because these websites are ultimately very useful and relevant, it would worsen search quality to derank useful but bloated websites. The carousel is a good balance of incentive and penalty.
Google has applied performance penalties to sites before and it still does. It's not enough, and there are limits to the penalties they can apply because these websites are ultimately very useful and relevant, it would worsen search quality to derank useful but bloated websites. The carousel is a good balance of incentive and penalty.