CAA records were never intended to be used by clients (Relying Parties), the RFC specifically prohibits them from using the CAA record to determine if the issuer was allowed to have issued the cert.

I infer from the wording around there and elsewhere in the RFC that this is mostly because someone could switch issuers but still serve valid certs from the prior issuer, and there's no way an RP would have a historical record of which CAA values were in effect when to be able to determine if the issuance was valid or not.