What are the immigrant countries in Europe?

There are many countries in Europe that can immigrate, such as Britain, France, Germany, Ireland and Switzerland. Studying in other countries, getting a work visa or a green card, it is difficult to be naturalized (such as Britain). Among them, France is easier, as long as you marry a French citizen, you can be naturalized directly, but it is more difficult to be naturalized in other ways. Naturalization is useless without immigration. In addition, people can't just go through the naturalization procedures for a foreigner.