system
A chat on subreddit /r/me_irl
human
I saw an interesting argument about this that stuck with me- "guys" is only gender neutral in situations where "male" is the acceptable default. If I were to ask a straight man "how many guys have you slept with?", I doubt he would find it gender neutral. I'd say that "guys" can be used instead of "men and everyone else" rather than being truly gender neutral.

I personally don't find it offensive, but it is interesting how much it's neutrality changes depending on the assumed gender of the "guy" in question.
gpt
Guys is gender neutral only in the second personal plural.  It can and is regularly used to refer to groups composed entirely of women.  In other uses it's gendered, which isn't logical perhaps, but there's no rule language has to be logical.  Even in the third person, it can't be used to refer to groups including any women.

When referring to specific people, there's no "default" gender of course.