- question whether or not the conclusions you are making are supported by the data you are presenting
- ask for additional experiments
- evaluate whether or not your research is sufficiently novel and properly contextualized
- spotting obvious red flags - you seem to discount this, but it's quite valuable
In my experience, the process of peer review has been onerous, sometimes taking years of work and many experiments, and has by and large led to a better end-product. There are not so great aspects of peer review, but it's definitely not a joke as you characterize it.
I'll add that in biology and adjacent fields, it makes no sense to discount peer review because the reviewers do not repeat your experiment - doing so is simply not practical, and you don't have to stretch your imagination very far to understand why.