<rant>
Hell, back in the 2000s, even web apps used native widgets, and we shamed websites that implemented their own UIs in Flash because they were bloated and inaccessible. Now we do it in Javascript and it's considered okay, even though all the same objections apply. And with Electron apps we've managed to combine all the worst aspects of web apps and native apps - they're slow, non-native and not cross-platform, and don't have text search, and still have to be installed.
</rant>
But the users' expectations are set by their cumulative (read: across all apps) broader experience. If a high percentage of your users have a certain expectation for Interaction X and the app is not that (tho' consistent within the application) those users will likely be disappointed.
Of course some components + UX are truly unique. Perhaps the crux of your killer app / killer feature. Unfortunately, this is not as often as most ppl think; thus too much time is wasted making unique those things which are better off frictionless and forgettable.