I'm going to try to explain this like you're five. I don't don't if it will work. You might not be quite at that mental level yet.

Show the bitcoin blockchain to the Average Joe, and he doesn't see a damn thing, just a bunch of letters and numbers. Better yet, show the actual bytes, not how it is interpreted on a block explorer. Understanding, interpreting, and verifying that blockchain requires an understanding of the protocol, and being able to do things like verify secp256k1 signatures and sha256 hashes (two bits of complex cryptographic math) in order to tell that the blocks are valid, the transactions are valid, and the outputs (coins) you receive are legitimate.

Monero is exactly the same damn thing. If you understand the protocol, and how to verify CryptoNight hashes and CryptoNote ring signatures (two more bits of complex cryptographic math) you can tell the blocks are valid, the transactions are valid, and the outputs (coins) you receive are legitimate.

It is a different protocol, with different cryptographic math, but from the point of view of verifying the chain, exactly the same.

You also don't know what fungibility even means as a definition. It means interchangeable. If the coins are all mathematically verifiable (and they are), and can't be attached to some unique and distinctive history (which the can't), then it is fungible. Whatever other gibberish you want to throw around in an ongoing months- (years- ?) long display of your own ignorance does not mean fungible, if it means anything at all.