You’ve made a lot of assumptions based on what? No one, not you or I or anyone but God can know how many Catholics or any other persons baptized in Christ have good spiritual lives. Catholics must to go to confession when we have grave sins to confess, although even minor offenses are good to confess, as well for the grace reconciliation provides us–which we know we will receive not merely hope we will.
That’s not all that Jesus said to Nicodemus. He goes on to tell him just what he meant by being “born again” in which he said nothing at all about any “personal relationship” with anybody. You are reading verse 16through your Baptist lenses and omitting verses that don’t line up with that interpretation. The true interpretation is that baptism is the initiation into God’s kingdom not a “personal relationship” with God–whatever that’s supposed to mean. Jesus commanded the Apostles to go and baptize all nations in the name of the Holy Trinity. He said nothing at all about telling people they need a “personal relationship” with anybody.
We Catholics do read and study the Bible and know perfectly well what Romans, as well as all the other books mean for us and our salvation, thank you. Bible study is encouraged in the Church. My parish has a Bible study every Wednesday morning for those interested. And we have special Bible studies in the evenings that cover one book at a time.
Gratitude yes, but more than this. When we cooperate in doing Christian acts of charity we are doing God’s own work through his grace and the power of the Holy Spirit. This engenders more grace in others and aids us in our salvation, for no one can please God who doesn’t obey him, doing what he has commanded us to do–what the Church describes as the corporal (bodily) and spiritual acts of charity.