What were the political commitments of the writers of the pre-WWI history you read? Could they have an incentive to characterize things this way?
Margaret MacMillan is a modern historian with a liberal world view and no ideological incentive to defend Bismarck, and in her phenomenal work The War that Ended Peace (2013) she largely supports this view.
The summation aligns with everything I've ever read from anyone about Bismarck and Kaiser Wilhelm.
Behind the Bastards has a pretty good couple of episodes on this little corner of history: https://podcasts.apple.com/ke/podcast/part-one-kaiser-wilhel...