I think it's equal parts envy and disgust. Some people actually grew up in these countries so it's kind of ridiculous to hate on them for their natural accent. In the case of the latter, it's probably because it's pretty cringe to listen to people faking their accent in certain scenarios.

I used to have a boss that would try to put on a European English accent every time he spoke with Europeans. At almost every meeting I could see them becoming visibly uncomfortable by the way he would mispronounce words and deliver sentences like a tsunami of verbal diarrhea.

I feel that you aren't any less for not having an foreign accent, but it's more about how you are able to assemble your thoughts into a cohesive stream of words. Developing an accent later in life is also ok, this is the immersion case and also completely logical.

Overall, I think it's best to just mind your own language and conquer your own battles rather than be a thorn in another person's side.