Articles that are not peer reviewed might as well be hearsay opinion. Science has to stand up to scrutiny, which is why there are journals and peer review processes, to weed out mistakes or simple BS.
There are pros and cons of peer review—the cons are that they inhibit real scientific advancement since the reviewers are established scientists defending existing theories and nowadays ideology.
https://theconversation.com/hate-the-peer-review-process-einstein-did-too-27405