/u/Aerandir provides us with his/her usual superior work with the comment you cite. The specific comment was as follows: "Note that we definitely can not just use the Edda (or other Icelandic literature) to find easy answers. This is not representative of popular belief, but a highly personal, warped account by Christian elites writing about their direct ancestors." To this we can add that there is an inclination to take a single document as indicating what people believed over several centuries and across a broad swath of geography. Even if the Edda literature could be taken as a fair portrayal of popular belief for the time the material was written in Iceland (which it is not!), applying the conclusions about popular belief to other centuries and places would be problematic. But as /u/Aerandir suggests, the Poetic and Prose Eddas require an enormous amount of source criticism because by nature of being written by people who were more or less converted to Christianity (as indicated by their literacy), and besides that these sources were already a step removed from popular belief in that they were written down as opposed to described orally.

All of that having been said, we must also acknowledge that there are simply too few dots to connect to understand "Viking beliefs" - the term you use. And yet, people are not going to walk away, simply, from the urge to try to understand the belief systems of the many people who lived during the so-called Viking Age. And because of the urge to understand, everyone - scholars and enthusiasts alike - are going to fall back on the rare, imperfect sources that we have at our disposal.

Careful source criticism is the key to good scholarship when dealing with the humanities. We must be very careful to understand the context of the literature during the period following conversion, and we must understand the temporal and geographic limits of those sources. The literature is flawed and rare, but since it is all we have it is all we can use to peer into that part of the past. We must liken it to looking through a mirror to see down a hall when we can't actually peer around the doorway to look down the hall ourselves. The hall is poorly lit and the mirror is terribly fogged, but since we are drawn to see what is down the hall, we use what we have. But we must never lose sight of the fact that our view is imperfect.