There are few fields that are universal and mostly free of bias due to their nature. Mathematics for one, due to how math works can mostly be free of opinion. Math is a just a set of logical rules used for measuring things. There are no opinions in such a field. Something either works or it you fucked up.
Other fields definitely are full of shady shit. I've spoke to plenty of researchers. I've been asked to review papers and journals before. Many of them admit that in some fields there's a lot of shit. There's a lot of evidence showing that some research that sets out to find discrimination against women, often ends up finding that men are discriminated against or at the disadvantage. Many of these papers get thrown out for X reason. Often times studies can be funded by certain people or bodies and if they don't see the results they like, they can just trash the entire thing. Stop funding it.
We shouldn't just ignore peer reviewed papers most of the time though. All research builds ontop of previously established findings. While it may be time consuming theres a lot you can extrapolate by properly analyzing them. All research can be critiqued, positively or negatively. Fact is there is no such thing as a perfect study. There aren't many research methods that are foolproof. All have their pros and cons. The biggest barrier being the immense amount of variables that play a part in certain things. Some things you can prove for certain, but bigger picture stuff, cause and effect, you can infer most of the time. It can be very hit and miss depending on the topic and focus of the paper.
