In the ethno-nationalistic sense, Sweden is not a nation state. In its current reality, Sweden is ethnically diverse and it (partially) covers the homelands of several peoples/"nations" in the ethno-nationalistic sense. The latter issue could, e.g., be solved by giving up most of what the Swedes in the South call Norrland. This would deplete "Sweden" of natural resources and make it even more dependent on high-skilled immigration to ensure that at least the tech industry industry in the somewhat larger cities keeps running.
If Sweden isn't Swedish because ~30k Sami live there, then China isn't Chinese because 50K Uzbeks live there. You're not arguing that Sweden isn't a nation-state, you're arguing that nation states don't exist, which is just silly.
You are introducing a straw-man argument here (that obviously ignores basic facts about population sizes of Sweden and China, so it's wrong on both meta- and object-level). But following that line of reasoning, Sweden is not an ethnostate because the Swedish population is ethnically diverse. E.g., more than a third of the population are either foreign-born or have at least one foreign-born parent. At the same time, the current borders of Sweden cover more than the traditional homeland of your preferred "Swedes". So apparently, you are actually arguing for a racist empire. Demographic reality is not your friend, though. Perhaps you will have more success some generations down the road. Try to sell the same story to the ethnically substantially different group of people who will consider themselves "Swedes" then.
How does this lead to the conclusion that Swedish ethno-nationalism is bad?