Non-native English speaker here. I’m defaulting to “they” or “one” unless it’s someone whose gender is known and is one of the two widely recognized today. Does that actually fall under incorrect usage of English pronouns?
>The singular they had emerged by the 14th century and is common in everyday spoken English, but its use has been the target of criticism since the late 19th century. Its use in formal English has increased with the trend toward gender-inclusive language.
http://www.npr.org/2016/01/13/462906419/everyone-uses-singul...
Basically singular they is used by everyone because it sounds and feels natural in many contexts. It's only a touchy subject when people assume you are using it to be "politically correct."
Style guides are changing, Washington Post just changed theirs to allow singular they.