What is the purpose of the ten Hail Marys in the Rosary if you should not focus on them?

Many Catholics pray the Rosary every day. This is very good. They are meditating on the holy Mysteries. What I don't really get is the ten Hail Marys. I am not saying that it's vain repetition. That's not even an issue for me at all. This kind of repetition is very good according to me. I am only thinking about the purpose of the ten Hail Marys. I myself have tried to pray the Rosary (and the Angelus) and always focused on the words of the Hail Mary and how it relates to the mysteries. The thing is: many people say that you should not even focus on the ten Hail Marys. It's hard to say prayers and trying not to focus on them. I am confused. There are books with added words to the Hail Marys which allow you to focus on the words of the prayer. It can take some time to learn how to say prayers and never focusing on them. THe Rosary can be difficult for a beginner. All kinds of prayer have things that make them difficult for beginners. The Rosary is bassically Lectio Divina with some added prayers. What is the purpose of the ten Hail Marys in the Rosary if you should not focus on them?