like it or not, canon law for the Latin Rite states that to receive holy communion the individual must have reached the age of reason, and be properly prepared and disposed, and the test of readiness is not thorough grasp of all Catholic doctrine, but the ability to distinguish between ordinary bread and wine and the Eucharistic species, belief and understanding, according to one’s capacity, that the Eucharist is indeed the real, sacramentally present Body and Blood of Jesus, and express a desire to receive the sacrament, and not under any canonical bar to the sacraments.
If you disagree with this canon, might as well disagree with all of them. Make up your mind. As I have said many times, I believe the Eastern Rite practice reflects better the theology of the sacraments of initiation, however, I am not in charge.
The differences arose from historical as much as doctrinal reasons, which will have to be dealt with if and when the rules are changed.
The difficulty comes in interpreting “prepared” “disposed” and “understanding” too strictly in regards to the capacity of the individual, and there the canon says to err on the side of conferring the sacrament. Baptism and confirmation should never be delayed on the basis of a handicap, physical or mental.