I want to place a disclaimer here that I've studied Paul's theories on economics (and the econophysicists in general) quite closely and found them generally compelling, so I'm not a hater. But there is something about this video that really just rubs me in the wrong way. And it's not about the vibes being reactionary (although Paul has often shown himself to be rather reactionary when it comes to trans rights in the past).
My biggest gripe with this video is how much of its conclusions are derived from correlating a few limited data sets and preconcieved notions. Paul correlates the UK fertility rate with unemployment, housing prices (divided by wages) and the existence of birth control. Then, he uses the correlation coefficients to conclude that high housing prices are the biggest factor in lowering fertility, followed by unemployment, then by the introduction of birth control. Also, he mentions that women have been getting more educated, but that this lowers fertility because of student debt, again bringing back fertility to purely economic factors.
I just think that this is really shaky ground that Paul is standing on here. I'm not saying that he's necessarily wrong, but I think Paul really needs to reign in his tendencies of throwing up some data and extracting vast conclusions about the whole of human society from them (cause he will do that later in the video).
Unlike many of the things Paul makes videos about, the falling fertility rates in human society is an extensively studied phenomenon even by liberals. It would be much better for Paul to actually bring in this research into his video instead of making his own conclusions from scratch.
Now from these statistical correlations, he talks about how late-stage rome also faced a demographic crisis which caused a collapse of slavery. Then, he ties this back to the crisis of contemporary capitalism. This part is interesting yes, but again, it's based on the shaky foundation earlier in the video.
He also goes on a strange tangent about how the tories promised the electorate about reducing immigration but actually increased it because they serve the capitalists who want cheap labor. This type of "left-wing" anti-immigration rhetoric has already been shown to be dangerous in the past, because the anti-immigration crowd is always looking for ammo, any ammo to attack and exploit immigrants. They don't care if they have to launder these attacks in socialist language.
He also doesn't even consider the possibility that having fertility rates below replacement could be continued in a communist society as well, since there is no need for a communist society to continually expand its labor pool. He simply considers sub replacement fertility to be a problem to be fixed (the preconceived notion) and suggests that socialist societies will use economic measures to restore the birth rate.