Except of few ideological mistakes, I would say, quite a lot of time was wasted on doubtful technical decisions ... One year was wasted on trying to make it as WPF application, .NET all that ... 5, if not more, years were wasted on making it work as Electron'ish like application (CEF was integrated). Evernote is a typical companion application - the thing that sits in tray and pops up as quickly as possible when need…
Means don't drop down to asm to save a few cycles. It doesnt mean "dont fill your 10fps GUI app with crap".
Today, it more or less should be killed-off as a phrase. There isn't anyone optimizing anything, let alone "prematurely"