The issue with "unicorn" failures is that a product can be really successful in objective terms (users, revenue, profit..) but still an investment failure, if it fails to live up to valuations.
So, if investors in 200X thought (and paid as if) the company had N potential... N becomes definition of success. They'll also, in all likelihood have already begun to spend accordingly to that N level. Failure of one kind leads to others
As I said, it sounds like there are fundamental company issues with Evernote, but it also could be that it's more of a failure to live up to expectations (we should have been slack!) than failure in objective terms.
..I know people who like Evernote.