Varies by jurisdiction of course. Under American law and similar systems the admissibility of a type of evidence is established by it having been admitted before, and the initial admission is based on the judgement of some individual judge.
It would also vary by use-case. Some regulated industries have specific standards required for an electronic signature — and hitting those standards is typically an add-on cost for systems like Docusign.
https://www.businessinsider.com/judge-ruled-thumbs-up-emoji-...