You're being silly now. There are sadly a lot of policies that are perfectly sensible but never get implemented due to their political nature. Land value taxes, for instance, are widely regarded as an excellent approach to tackling extraordinarily high property prices, but never get implemented due to the vested interests of existing property owners. Similarly, when the state pension was introduced in 1908, life expectancy was 40 for men but you had to be 70 to get the pension. This was changed to 65 in 1928, when life expectancy was about 55, and it didn't budge until 2020, when it rose to 66, at which point life expectancy was now comfortably over 80. So the pension age has risen 1 year in response to a growth in life expectancy of about 30 years. It's illogical, and yet any attempt to change that gets rapidly beaten down by a portion of the electorate that vote in huge numbers.
Immigration is similar I'm afraid. As I said, over half of the world live under autocratic leaders who place great emphasis on restoring their country to some preordained era of greatness. They also rail against the so-called metropolitan elites that do down the working classes and actively deride globalization (and globalists) as enemies of the people. I'm sure you can recognise some of the language and behaviour of Johnson here as he (and Brexit) have undoubtedly been influenced by the likes of Erdogan, Putin, Bolsonaro et al, just as Trump was. Similarly, Macron has to veer right in order to fight off Le Pen. This is why even though rejoining the EU would make logical sense, Starmer won't even entertain it, much less a liberalisation of border restrictions.
I'm under no illusions as to the realities of the world and don't expect to ever see open borders outside of its marginal implementation in the Schengen Zone (which, as you can perhaps imagine, I regard as an incredible political achievement), but that doesn't mean that I can't see the evidence that crosses my desk each week about the benefits of (more) migration and the tremendous waste our nativist approach to things creates.