By the time you read this we've had the US presidential election, the bellwether of the direction the West is taking -- whether towards liberal & humanist values or a retreat into conspiracy theories, insular nationalism, and turkeys voting for Christmas. Not that the losing side turned out to exactly be paragons of incorruptible and dutiful good governance. One day maybe we'll appoint somebody who's fit to hold the office. (Other countries are doing better, but the overall liberty trend is downwards.)
You may have wondered what would happen if all the world's borders were open -- that is, the EU model of freedom of movement applied globally. According to one analysis it would make the planet nearly $80 trillion richer. That's ten thousand dollars a head if distributed evenly, so not to be sneezed at. Read about it in The Economist here (you can register to get free access to the article, or look at the archive.ph snapshot without the graphs here).
An additional benefit is we could stop spending money on war. The total cost of Putin's invasion of Ukraine to date, including reconstruction of Ukraine's damaged infrastructure, is now more than four times the entire amount spent on the Apollo programme after adjusting for inflation -- and before factoring in the spin-off tech benefits of the Moon landings. It's often said we shouldn't waste money on AI, or particle research, or space exploration, or whatever, until we've sorted out problems here on Earth. Well, start with national boundaries and then we can go to Mars and do the other things and still have trillions of dollars left to save the whale.
It happens I think the cultural benefits of full freedom of movement would be even greater than the financial ones. Intolerance thrives when people live in a racial and social bubble. The more you meet people from other walks of life the more you appreciate that our real identity is human, not national or religious or ethnic. And people from different societies bring different ways of looking at a problem. There are so many win-wins from international cooperation.
A criticism is that having open borders would be radically disruptive. So it would. But look at the inequality we have now, the division, the frothing hatred. When things build up to that kind of pressure you get wars and revolutions in which people are killed in the thousands or millions just for who they are. With the growing climate crisis the situation will only get worse. Isn't it worth looking for a soft revolution in how we live that could avoid all the atrocity and that after a decade or two of upheaval would yield a richer world for all?
It won't happen, of course. More likely the 21st century will go along the same lines as the 20th only with even more monstrous tech to fuel it all. There are plenty of dark clouds and few silver linings right at the moment. But don't let future generations say we never even tried. We only get a good future if we strive to bring it about. Here's Konstantin Kisin on that very point:

