The irony disappears when we let Paul define what he means. In the same letter, Paul says, "Circumcision is nothing and uncircumcision is nothing" (1 Cor. 7:19), which agrees with the decision of the apostles in Acts 15 that Gentile believers were not required to be circumcised.
Paul is not telling believers to ignore God. He is distinguishing between covenant signs given to Israel and the commandments of God fulfilled and taught under the New Covenant. That is why he can also write, "Neither circumcision counts for anything nor uncircumcision, but a new creation" (Gal. 6:15) and "faith working through love" (Gal. 5:6).
If Genesis 17 and Leviticus 12 remain binding on all Christians, why did the apostles refuse to place circumcision on Gentile converts in Acts 15? The real question is not whether God's commandments matter, but which commandments Scripture says remain binding under the New Covenant.