John 3:3, 5, and 7 are very important verses, if hypothetically speaking the Bible is true. JWs who want to be in the kingdom of God, even if as earthly subjects of the kingdom, should very carefully think about those verses. Those verses are saying that in order to enter into the kingdom of God people must become "born again" and/or "born from above" (the latter being an alternate translation) and be born from spirit.
By the way when the gospel of Matthew says the "kingdom of heaven" instead of the "kingdom of god" it isn't saying the kingdom is only in heaven. It is using a substitute word for "God" because that gospel book is written for a Jewish audience - including Jews were were cautious about often using even the title/name "God". The Gospel writer might also be saying "kingdom of heaven" to convey the idea that the kingdom receives its authority from heaven (that is, from God in heaven).
If JWs were to realize that the Christian Greek Scriptures is speaking to all Christians and all prospective Christians when it talks about being "born again"/"born from above", "born from spirit", being part of the new covenant, and being sons/daughters of God, then it would likely make reading the Christian Greek Scripture impart a much greater emotional impact to them. At least that perspective has such an effect upon me when I (despite being an atheist ex-JW) read it from that perspective while imagining that the Christian Greek Scriptures is true!
From the point of view of the NT being true, the WT is doing a tremendous disservice to JWs (and prospective JWs) when it teaches that only a literal 144,000 humans become part of the new covenant!