i don't see what's wrong with guys, it's a generic collective term for a group of people to me, informal but totally inoffensive.
however i do not like inappropriate terms of endearment.
i realise there are regional differences, but i felt a bit miffed when the 2nd vaccinator called me my dear.
i think there is a sexist element, as if patting a little girl on the head. he would not say it to a man of the same age. so he is assuming some kind of superiority over me, which is patronising.
he was a middle-aged man, probably younger than me. as an educated person, ?pharmacist, i think he should know better.