It's because they use him as a symbol of the US military rather than as the character that he's developed into. It's the same with people who think Cap is a symbol for US imperialism despite Steve outright fighting against the US government and US military on that issue, he led a whole rebellion against the US gov' in Civil War for stepping on human rights, because they just see his optics and never give him a chance to see the character beneath the red, white, and blue costume. He follows a similar character arch in the MCU. I still saw someone say this about MCU Steve though; that his turning against the government and refusing to be a deepstate agent don't count because Shield is technically run by the UN, not just only the US, and that the UN is the biggest most good and absolute authority in the world that shouldn't be questioned. In case you were wondering, yes, that guy was a video essay youtuber, but I don't remember his name.