Your profile says that you're "Splitting time between UK and Japan" so I assume that you're familiar with Windrush, Home Office hostile environment policies, and the Rwanda asylum plan? Those are deadly sharp edges.
Turning to more mundane issues such as applying for residence visas and dealing with border agents - The experience is consistently, cheaper, faster, simpler, and more competently and courteously handled in Japan than in the UK. It's not even close. If you have never had to deal with the UK Visas and Immigration office at Lunar House in Croydon, consider yourself lucky.
For sure, there are scandalous failings in Japan - child custody issues, treatment of asylum seekers, housing discrimination. Something should probably be done about the snooty restaurants too, I guess. But to point to Japan as particularly xenophobic, on the basis of time spent between UK and Japan is untenable.