None of your arguments address his main claim which is that decentralisation should be considered a means to an end and not an end in itself. Which makes sense

None of your arguments address his main claim which is that decentralisation should be considered a means to an end and not an end in itself. Which makes sense to me, if you just use a system it can be hard to tell for sure if it is centralised or not, which makes it an implementation detail not a feature. Though there are definitely features that are easier to guarantee in a decentralised system, as well as features that are easier to guarantee in a centralised system, so it makes sense to look at it as a trade-off.