Why is everyone so negative here?

Guilt of imperialism and an attempted shift away from nationalism following ww2 led to this “diversity is strength” sophistry that seems to have driven policy until now. It’s just incredibly naïve to think you can have a massive influx of, say, Somalians (who, for all intents and purposes, have an objectively inferior culture by any germane metric) and then expect locals to be happy when they refuse to integrate. For a lot of native people who maybe haven’t the capacity or time to think about it as much, they deeply mourn their culture and don’t WANT it diversified or emulsified; and their heuristic becomes “Somali individual inherently bad” as opposed to the more nuanced but I guess less socially reprehensible “Somalian culture is immiscible with ours” - tribalism and often defiant refusal to integrate obviously aggravates things. Normally, most would have no problem with a lovely Somali in Somalia 🇸🇴because he/she isn’t infringing on their way of life, but now the heuristic has changed. We love globalism. You can bury your head in the sand as much as you want, and mask your naïveté with moral outrage, but the fact of the matter is, whatever your politics, if you let in a never-ending cascade of low-skill individuals from countries all over Africa, the Middle East, South Asia etc etc - each with vastly different cultures and religions (and other metrics such as average IQ, English language proficiency, treatment of women, religious rites and garb etc) - then you’re going to alienate more and more of your native citizens as they wake up, and the melting pot you have created will scald you. It isn’t a dystopia yet but it’s coming if something isn’t changed, and the lack of said change is why people are expressing the negativity you mentioned.