A filter that does filter out the vast majority of obvious noise is very useful even if it lets something through. And the current peer-review does that, it throws out almost all of the spam; it pushes useful work of lower quality/impact down to less selective venues (generally with more specific subfields, so that I can read impactful work of domain X and less impactful work of subdomain X.2 but not X.1 and X.3); and even for accepted papers the process often results in significant improvements to them as a result of the reviews.

Explicit fraud isn't that common, since it does have risks to the submitter that far outweigh the (limited) benefits of getting an extra publication on your CV.

> quite literally anything can be published

I've got a stack of rejected papers that beg to differ.

> Isn't the point that they serve as a basic filter for obvious noise?

Yeah, and obvious noise is usually rejected. But sometimes it is not so obvious what the noise is, and that's why the scientific process is bigger than the peer review system.

> Isn't the point that they serve as a basic filter for obvious noise?

Totally, there is a lot to fix about it. But if you really want to put your effort into changing the system, I don't think you should focus on peer review. Destroying the business model of journals is where I would start.