I've done a docusign implementation, and I don't really agree with them. Their API is fine honestly, I think their documentation could be better and some things are named awkwardly. But the implementation really isn't hard, my only real complaint is that when we did it they pushes the DocuSign connect service really hard, which honestly was kind of a waste and didn't live up to many of their promises, but that's normal b2b upselling. It's a normal API, and definitely not as bad as this person makes it seem.