Hey @crypto.piotr, they asked you the million dollar question!
If it were easy to make it clear to those who know nothing about the functioning of the blockchain today we would have had a mass diffusion of everything that revolves around this technology such as crypto currencies.

However, I understand your frustration because that's what I feel when I try to explain blockchain to my 70-year-old father.
I usually make a comparison with our bureaucracy, we Italians are famous for this.
So I tell my dad that our data is kept in public offices and we need an intermediary to print our documents for us.
Instead, with the blockchain we can access our documents alone, because our data is kept in a secure database shared with all the others who, like us, have entered their data, and this is precisely the guarantee that our data cannot be modified without our permission because we all watch over everyone's data.
So each of us can manage their data without it being kept in a central archive.

Another example is the food supply chain because my father is greedy so I explain to him that every step of the food, from cultivation to harvesting and finally to the shelf, through the blockchain is all verifiable by everyone, not only by professionals but also by us. consumer citizens.
Traceability is guaranteed.
While with the old systems the data can be forged, perhaps altering a product expiration date, because that type of database can be overwritten.
On the other hand, blockchain-based systems guarantee the truthfulness of the information because once entered it can no longer be changed.
Then, when I have to explain to my father that everything can be controlled with an app and a QR code, I start having difficulties because he doesn't have a good relationship with his mobile.
I hope I was helpful, but simpler than that I just can't find other words.