People often confuse the terms ‘generalizing’ and ‘overgeneralizing’ as if generalizing were a bad thing. It is not. All of science depends on generalizing based on specific cases. You’re able to put on a new pair of underpants you’ve never seen before because you know how to generalize. The problem is not generalizing, but overgeneralizing, that is, drawing too general a conclusion from too little evidence.
A common example of overgeneralization is prejudice: a white supremacist meets two black people and draws conclusions about all black people based on those two. A person meets three red-haired people and draws conclusions about all red-haired people based on those three. A person meets one person with autism and draws conclusions based on all people with exceptionalities, etc., etc. In every case, one overgeneralizes, that is, one draws a conclusion that is too general based on very limited data.