The person without the Spirit does not accept the things that come from the Spirit of God but considers them foolishness, and cannot understand them because they are discerned only through the Spirit.1 Corinthians 2:14 NIV
While I was in the Navy I spent a few years stationed in Sicily. One of the challenges of living there was that I did not speak Italian. I eventually learned enough to be able to shop and play tourist. But when I would try to have a conversation with one of my Sicilian neighbors or someone else from the community, I was at a loss. I could understand little of what they had to say. There is no doubt I missed out on a lot because of that failure to communicate. I found it to be much more rewarding to hang out with someone who understood the language and could interpret it for me. That greatly enhanced the experience of living there.
Understanding Spiritual Truths
I believe that is a rough example of what Paul is talking about in this passage. I am a physical person and can understand physical concepts. Some come easier than others, but I have the capability of eventually grasping most of what I am told. But God inhabits a spiritual realm that is foreign to my physical mind. And, on my own, any discussion of that spiritual reality and the truth it contains sounds just like gibberish, it makes no sense at all.
But God has given his Spirit to his people. And his Spirit serves as an interpreter, helping us to understand the truths contained in the spiritual realm. He does not instantly give me a complete revelation of all spiritual truth. But he does give me insight into it as I study and grow. So long as I walk with the Spirit, he will teach me what I need to know. In the same way that traveling through Sicily with an experienced guide would help me to make much better sense of what I encountered there.