Yes, this is a problem. It may be difficult to decide in exactly which cases it's "bad", but there are definitely answers without the necessary experience or knowledge to support them. (I don't think it's helpful to hunt for examples here; it feels a bit too close to name-calling.)
This is completely unsurprising. Sure, it's rare for people to knowingly post bad answers, but we often don't know what we don't know. As long as people are allowed to post confidently clueless answers, they will do so. And as long as those answers are present, the sufficiently convincing ones will gather upvotes - there will be other people who have similar gaps in experience or knowledge.
Realistically, I think the only solution is to actually enforce the back it up policy, e.g. with deletion of answers. There is ample precedent across the network for going beyond "not an answer" deletion. From the network-wide FAQ on deletion (in the "What are the criteria for deletion?" section, after covering "not an answer" and such):
These are general guidelines; some communities in the network may uphold more specific reasons to delete posts or not. For example, on Puzzling.SE, answers to a puzzle without explanation are subject to deletion, and some technical sites will delete answers which are not only wrong but also harmful when tried.
This is, of course, not an easy thing to do. A lot of the judgments to be made are difficult. However, I see no way around it, so I think it's a tough path we are forced to follow if we wish the site to flourish.