Even with talks on Spirit and the importance of renewal, Nicodemus still didn't seem to get it.
However, in 3:10, Jesus pointed out that said concepts should be stuff that Nicodemus should be familiar with. Especially given that Nicodemus is one of the leaders of Israel -- likely a teacher. The concepts Jesus talked about on Spirit and renewal have multiple roots in the Old Testament that God intended to showcase. For instance, David's repentance of sin, promises of a renewed heart from Ezekiel 36, and even Deuteronomy 10:16 that refers to the need of circumcision of hearts. Since Nicodemus is an important leader, Jesus knew to tell Nicodemus (rhetorically) that despite being an important teacher, he hasn't known such topics. Kinda like a pre-calculus teacher telling one of the students that he or she should know arithmetic. From the following verses, Jesus seems to be more on the concern side and willing to help Nicodemus learn what he should have learned (rather than trying to throw Nicodemus down).
Relating to the comment, Jesus mentioned in 3:11 that some concepts that God shared (from various time periods) have been rejected by the Israelite people. In essence, Jesus explains that sometimes not knowing is not because of difficulty learning but because of not wanting to learn said concepts in the first place. Jesus does not want Nicodemus to go down the same path as the people who decided to throw out said concepts.
Additionally, Jesus explains that if Nicodemus does not trust Jesus's explanation in 3:12, he may have difficulty learning heavenly concepts. Jesus used terms like "born again" and "wind" and "water" to help Nicodemus get a better idea on the concept of the need of renewal. Heavenly theological concepts are difficult to understand (trust me, I've been there before); hence why Jesus likes to use analogies.
Nicodemus has come so far to learn that what Jesus says would be important and that he should have a chat with Jesus. But Jesus doesn't want the drive to learn to stop. Similarly, especially if one hasn't known Jesus a lot, we should strive to learn the truth about God's renewal, which Jesus would explain later.