Fundamentally countries have a right to self determination and that includes the future direction of the countries, culturally, economically, etc. So long as it does not encroach on other countries' sovereignty.
In the US we actually had a racist immigration policy, the Chinese Exclusion Act [0] because it was actually applied to a single race created by actual racists. Do you see the difference?
And yes, the Chinese exclusion act was by definition racist... But no one in any major western country is talking about excluding one race or even nationality of people outright (Trump talks about "pausing" immigration from conflict zones).
People do speak about controlling their legal immigration and deterring illegal/undocumented/etc. immigration (but pretty much all countries do have visa requirements (or inter country-region agreements) --even those who mainly export workers.
I don't actually consider the UK's immigration policy as racist. Short-sighted, definitely. but racist? Definitely not
But these immigration and cultural issues aren't necessarily racist. The weight behind anti-immigration movements includes other social/cultural/economic opinions, in addition to flat-out racism.
There are aspects of their history which was racist and the treatment of people of Korean descent living in Japan for generations is debatably racist (more ethnicist than racist) but their immigration policy, I don't think is racist just because they are very strict about accepting new immigrants and naturalizing people.