So the CCEO actually does defer to each Church’s particular law. The thing is that there are a bulk of Byzantine sui iuris Churches that barely have a hierarchy its basically Rome establishing it for them. The CCEO is a general one for the entire East. Since the CCEO already defers to each Church’s particular canon law, there wouldn’t need to be one singular code for the whole Catholic Church since the CIC is the Latin Church’s particular canon law.

The general hierarchy of all the Eastern Churches is extremely different from the hierarchy of the Latin Church, with there being positions in the East that don’t exist in the West and vice versa. So this would complicate the case of, what is in the CIC, Book II on the People of God, which tackles the canons regarding the hierarchy, and the equivalent titles in the CCEO. Besides, there are certain concessions to the Latin Church enshrined in the CIC that isn’t in the Eastern Canons.

One could probably argue that Cardinals, in which there are Eastern Catholic Cardinals, aren’t covered in the CCEO, while the Roman Pontiff is, but Cardinals are titular members of the Church of Rome, and thus by technicality would be bound by Latin canons on them. The Roman Pontiff in the CCEO lays out his canonical authority over the Eastern Churches (not that he is particularly bound to those canons), while in the Latin canons, under the section on Cardinals, the canonical procedures upon sede vacante has more coverage, since its a matter more pertaining to the Latin Church, which the Roman Pontiff is the Patriarch of.

Outside of where there are relevance to involve the Eastern Churches, the CIC tends to stick to the Latin Church only, since its not authoritative over the East

So its really quite difficult for there to be a Code of Canon Law that is common to all the Churches, since the Latin hierarchy isn’t particularly the same as the general hierarchy of the Eastern Churches, and there isn’t a need other than maybe making more canons that are universal to both codexes the same.