I think the better argument against the CAP theorem is that while it is true, is it not really that useful. If you have a database with nodes in three data centers, it is much more likely that one of the data centers becomes disconnected (partitioned) from the rest of the internet, rather than that the internet itself is partitioned. In this case, a CP system can still remain available to the internet, it just can't also remain available to the nodes within the disconnected data center.
https://foundationdb.com/white-papers/the-cap-theorem