Sorry to disappoint you, but that is not referring to the Gospel, but to doctrinal matters.
Paul is speaking to believers about growth ('milk' vs 'meat'), not the Gospel.
The Gospel is understood by unregenerate man because 'faith cometh by hearing and hearing by the word of God' (Rom.10:17)
Please spare me anymore Calvinistic proof texts, I have seen them all over and over again.
More to the point, this is a thread on eschatology. However, it is an old and tired thread. Maybe a rousing calvarm fight will put it out of its misery.