To understand and reconcile this verse and the verses Paul gives which directly oppose this, most people fall into error. They either say Ezekiel 44:6-9 no longer applies (wrong to some extent), or Paul was wrong. Yet those who say Paul is wrong are wrong, because if you see in Acts, when Paul went before the entire body of believers in Jerusalem with Peter and other members there such as James, Gentiles were not required to be circumcised.
Then some of the believers who belonged to the party of the Pharisees stood up and said, "The Gentiles must be circumcised and required to keep the law of Moses." - Acts 15:5
This is shot-down by the Jerusalem church leadership, James states:
19 “And so my judgment is that we should not make it difficult for the Gentiles who are turning to God. 20 Instead, we should write and tell them to abstain from eating food offered to idols, from sexual immorality, from eating the meat of strangled animals, and from consuming blood. - Acts 15:19-20
James was Christ's brother, and a Jew who converted to the original "Messianic Judaism", so if we want to reject what he said on the issue, I think we have deviated from Christianity entirely. At which point, we are practicing Judaism with a little Jesus mixed-in, not Christianity.
From that statement we can make a better argument not to eat blood sausage and have blood transfusions, than we can for circumcision.
How do you reconcile the two viewpoints, OT and NT since both are true?
The key to reconcile the viewpoints is to learn prophecy correctly. Not many people get their understanding of prophecy correct. I think it's only possible if you're willing to let God teach you and not presume interpretation of other men, or interpretation you create yourself.
To know truth prophecy, you do not go to a prophecy teacher who teaches it. This does not work because they all say different things and who knows which you believe?
How to learn prophecy from God:
- Ephesians 1:17 - Required prayer to get wisdom from God. Only God can teach you things of scripture, not man or the world at large, only God. Read Proverbs about wisdom and also James which teaches us how to ask for it.
- Romans 1 through 12 - Andrew Wommack study materials I would suggest, but if you read it enough God will show it to you, if you're not leaning on what people have told you in error; the key to learn is salvation by faith and grace, along with mercy, which allows us to conclude we are "the righteousness of God" and actually believe it (stating it is meaningless unless you believe it by the spirit)
- Galatians - Read it, again and again, it teaches grace and justification apart from the law.
- Hebrews 6 basic doctrines of Christianity, you need to learn these six listed from the rest of scripture and be able to fully explain them without error
- 1 Corinthians 13 - Should understand love. Without understanding love, a person can never understand prophecy in scripture. This is because there is a prophetic spirit of fear sent by satan. Love casts out all fear, so a person has to be rooted and grounded in God's love to know prophecy.
- Study on Blood Covenant - Genesis 15; Exodus 12; Exodus 24:8; and others.
- Jeremiah 31 - New Covenant prophesied
If you know all this, and believe it just as the writers believed it, then you can start prophecy and get somewhere. Prophecy can never violate any of those concepts, otherwise it is false prophecy.
What you will eventually learn from true prophecy is that eventually there are 2 domains in heaven. New Jerusalem, and an Earthly Paradise kingdom. Quite likely, everyone in the Earthly end of things, will actually be circumcised in the flesh. While I have not studied this a great deal, I would begin my research in the matter going that direction. The later chapters of Ezekiel deal with this Earthly domain of heaven / eternity.
Those living in the heavenly domain of eternity, New Jerusalem were circumcised by faith and given new incorruptible bodies created by God... this is the Church, you and I. We don't have to circumcise our flesh. I am not even sure we will have genitals when we are raised? I don't know, if we do, they will not be used.