No open source startup is going to win there because it's about entities and process, supported by technology not technology on its own. The technology is absolutely worthless without the framework and legal entities surrounding it. It's a unique position no one really understands that well.
A digital signature is a legal construct that stands up in court.
The movement might have begun, but you need to change your perception. You have to stop talking like a technocrat and address the business problem that signatures solve.
Not losing it is another.
The people to preserve trust with are all potential signatories (ie. the public), not the initiating counterparties. Because there are many more of them.
Of course this reputation problem is one you'll share with banks, PayPal and every other "official" type entity that phishers want to jump on.
Now most "Docusign" communications go straight to my spam folder or /dev/null if arriving by email and not from (forwarded) a whitelisted business I already have a relation with. Those that come directly from Docusign (as sender even if DKIM passes) are ignored unless I think there's a reason to be contacted.
Docusign is one of the juiciest spoofing targets for phishing attacks because people act rashly to what they think is something requiring a signature. They also have no timeout on repeat sends, relentlessly spamming users to sign something, which makes them look exactly like, well.... phish-spammers.
Try not to make these same mistakes as Docusign.