Does that mean you shouldn't read any of the others? Of course not. You should at least read "Dune" and "Dune Messiah", although I found "Dune Messiah" dull. Reading "Children of Dune" without at least having read "Dune" would only confuse you.
Do you need to read any of the new Brian Herbert books? No. You certainly don't have to read the first three prequels. I found they jarred a little with the original series, they have many of the same characters but they're written differently enough that they seem wrong when you cross over between writers. I enjoyed them, but ultimately they're useless.
I thought the machine wars trilogy of books were pretty good by themselves, as pulp sci-fi apocalypse books go, and although some characters have the same last names, there isn't too much to connect it to the original series (except the planet "Dune").
But I'd find it hard to suggest you should read the sequels, in the same way I couldn't suggest you read the final two books of the original series.
But as a completist, I just couldn't help myself.