Even if you don't get open borders, the fact that we have all these treaties which force free flow of capital across but do nothing to allow easier flow of labor across borders is a huge problem. It allows nations with crappy social and political systems to undermine labor welfare and protection policies in better political systems without facing repercussions for it. Unsurprisingly, the asymmetric flows of capital and labor forced by trade agreements play right into the hands of benefitting capital owners across the world at the expense of ordinary workers.

I don't believe completely open borders are necessary or even possible, but every trade agreement that forces free flow of capital (and prevents duties on imports, etc) needs to come with equivalent labor protections as well (massively increased flow of people across borders, and not in a "you're a second class resident who can be deported at your employer's whim" way, or alternatively, removing import duties only as long as laborer a on both sides of the border receive equal labor protections of the law. So if country A offers a minimum wage, it is allowed to impose duties as long as the wages being offered to the workers in country B is less than the cost of living adjusted equivalent salary in that country. )