Yes, your grandson can make a website, just as you can make a pizza, but can you make a real Neapolitan pizza in your oven and with supermarket products?
We think the answer is obvious. We can make our own shirt, but we can't sew it better than a couturier. We can eat a frozen pizza from the supermarket for dinner and it will still be a pizza, but it will not be comparable to that of a real Neapolitan pizzeria. There are subtleties in everything and everything must be learned.
Having a website is not enough, it's like having only the body of a car, you also need all the other parts. So, for example, at a minimum SEO, good site design and also good site usability.