>because it does seem odd that any entity would be capable of judgement above God
God alone holds judgement. The accusation of the demons is not fair or even truthful. Nonetheless, to abandon us to the demons is God's punishment, if we have remained their slaves during our life.
>and it just sounds like another form of purgatory tbqh
Purgatory is after the particular judgement: those who are saved but are not perfect yet (because of having venial sins or worldly attachment) must go through purgation before they can enter Heaven. The aerial toll houses are about the particular judgement itself: those who fail at any of the toll houses are dragged into Hell, those who pass through all of them have conquered the demons and can be with Christ.
>but then I'm left confused as to why it's been defended by so many people
Some defend the teaching against those who (wrongfully, in my opinion) attack it as being a gnostic heresy that crept into the Church. Some defend the teaching wrongfully though, by proclaiming it as dogma and accusing of heresy anyone who does not hold to it (or even those who hold to it but not in the very detailed form that can be found in the teachings of some saints).
>Pic related is supposedly a huge tome defending the tollhouse theory for example, so I have no idea what's going on.
It's not an amazing book. For a good chunk of it, references to angels and demons fighting for our soul when we die, and references to the demons dwelling in the air, are automatically taken as proof of the toll houses. Some of the content is outright false as well - for instance, the homily of Cyril of Alexandria that is cited as describing the toll houses is in fact a forgery.
Honestly it was a big waste of money from my part, and I strongly regret buying it.