Why is saying there 2 genders bad

From what I understand people can be (cis or trams) male or female, nonbinary (which is a lack of gender from what I understand rather than a gender) or stuff like gender fluid, which from what I understand is switching between the 2 genders so I'm not sure if it counts as another gender, I know the title doesn't sound good but I guess I just wanted to gain attention to get some answer to my question, I don't want to start drama, I'm genuinely curious and uninformed maybe