Taking everything into account is difficult, especially when you have no idea exactly what you aught to be taking into account. Even if you manage to do that exactly right, there is still publication bias to deal with. And if you are using science for practical purposes, it's even harder to make sure that the research is answering the right question in the first place, Sieben's comments sound anti-science...but really they are frustration directed towards a real problem. There really is a lot of bad science out there, sometimes it is even published in top journals - and even good science is usually extremely limited insofar as you can use it in practice.

I think it's just important to remember that while scientific papers should be given more weight than almost every other source of evidence, that's not actually very much weight. You can't instrumentally rely on a scientific finding unless it's been replicated multiple times and/or has a well understood mechanism behind it.