I think the counter-point to this (Which you kind of bring up, "what to watch out for") is that success is often more about not losing than winning. So reading about other people's failures can be very helpful in ensuring you don't lose.

The other thing is that although a failure may be unique overall, there are undoubtedly common aspects among failures. So I feel like you can sift through a lot of failures relatively quickly once you find some of the common patterns.

For example, one of the most common failures of startups is no market for the product. Therefore, if you're researching a failed company and it seems like this is the case you can assume there will be little value in this failure and skip ahead.

Another possible technique following this line of thinking is to apply filters. If they failed before they reached x point, you can skip ahead.