How do you bootstrap a node in the face of conflicting history? How do you handle network partitions?
There are also open question surrounding security, prevent actors from colluding and so on. Most other blockchains do not even bother. At least the Ethereum people have the ambition to have something practical. Let's study the design when it you can make an eth transfer with it.
These discussions are like when in a discussion about uranuium waste management someone inevitably cries about how we should just scrap it and go with fusion energy instead.
Great idea, but let's have something working first.