I have found a solution that works, but only for an application called SnagIt, the process might help elsewhere.
SnagIt allows the addition of an Application to its Share menu and will only allow applications that are "supported" to be added.
However I do agree that the omission of native sharing to Evernote from within MacOS is serious - what is the point of a note taking application if one can not add any form of document/image/file seamlessly!
Evernote is definitely falling behind the curve and this raises serious questions regarding their commitment to existing paid customers with long term investment to the application in terms of both data stored and workflows adopted