Yeah, I find it annoying when people presume to refer to an unknown person as 'He" or "She". It's especially annoying when a writer randomly alternates genders throughout their document. Pandering much?

The solution is the firmly established use of the singular "They": https://en.wikipedia.org/wiki/Singular_they

The singular "They" has literally been used in the English language since the 14th century, and its usage is well-understood. Any English teacher who dissuades you from its use should be stripped of their credentials, because "they" are an idiot.