As you pointed out, Ranke and other historians of the time prized prized factual-based evidence as the only way to write entirely accurate history. This may seem positive at first, but it's essentially an impossibility, as historical writing is inherently subjective. First off, a historian simply can not include every relevant or semi-relevant piece of evidence and therefore has to choose which facts best are most relevant, which will always be a subjective process. Additionally, facts are only beneficial when presented in a certain historical context. As such, it is up to the historian to interpret these facts, which is again a biased process. For example, I could look at factual historical evidence, such as a chart of the growth of suburban housing construction following WWII, but without being able to place it into a larger, subjective historical context it's of little real interest. Essentially, the historical process of Ranke is obsolete because it is too naive a way of examining history and historical writing, and even if it were not, it would be impossible to fully utilize. When writing history, there will always be some bias on the part of the writer.

I hope this was helpful. I'm a history undergrad interested in historiography. If this interests you, I'd recommend EH Carr's book What Is History?, especially the first chapter. At one point he mentions that while facts are necessary for a historian, they are not the main function of a historian - it is how one chooses to interpret facts that is important - and that is what Ranke specifically ignored.