I am pretty sure there is also a political component at play here. There was a time when there was an actual political debate about who could destroy the enemy the most and therefore had to have the most and the meanest nuclear weapons. This is no longer the case. Instead everyone is in complete agreement that nuclear weapons are inherently bad. Of course superpowers need a couple of nukes because that's what superpowers do (right!) but it is not acceptable to boast about them like it was 50 years ago. And if you cannot boast about how big your thing is, then there is no particular point in having a big thing in the first place.
Of course, those who need to know will know. But because of the many technical reasons you have explained in this article, experts in the field will not be impressed by ever larger nuclear weapons. Big bombs like Tsar Bomba were probably always more about politics than strategy. And since that kind of politics is now gone so is the need for ever more powerful nukes.
I am pretty sure there is also a political component at play here. There was a time when there was an actual political debate about who could destroy the enemy the most and therefore had to have the most and the meanest nuclear weapons. This is no longer the case. Instead everyone is in complete agreement that nuclear weapons are inherently bad. Of course superpowers need a couple of nukes because that's what superpowers do (right!) but it is not acceptable to boast about them like it was 50 years ago. And if you cannot boast about how big your thing is, then there is no particular point in having a big thing in the first place.
Of course, those who need to know will know. But because of the many technical reasons you have explained in this article, experts in the field will not be impressed by ever larger nuclear weapons. Big bombs like Tsar Bomba were probably always more about politics than strategy. And since that kind of politics is now gone so is the need for ever more powerful nukes.