Some prayers in the Catholic church can be performed by rote and have absolutely no meaning at all when performed that way.
It’s not because of the prayers themselves though. It’s the intentions and the attention of the person praying that matters.
The rosary is a great example. I know people who say one every day. I’m sure that if they wanted to, they could just say the rosary in the back of their mind while balancing their checkbook and it wouldn’t mean very much then. But that’s not what they do and that’s not how it is intended to be done. The rosary is meditative, in order for it to mean anything, you have to concentrate and focus on saying it and what it means.
I liken it to other meditative practices like breathing exercises in a martial art or yoga. The purpose of long breathing is not so much physical as it is mental. The idea is to focus your entire attention on the simple act of breathing and nothing else. It is very difficult and can take hours to actually achieve, but once you do, your mind is completely free and calm. Once you have it under control, you can focus it anywhere you like and not be sidetracked by distractions.
The rosary is the same. As you say the rosary, concentrate on each word of each Hail Mary. Think about what the prayer means and try to internalize that meaning in your act of prayer. Think about the mysteries through each decade of the rosary as you say it. Focus entirely on the act of praying the rosary and use it to drown out all distractions. The purpose of the beads is to relieve our minds of the burden of counting our prayers, like an abacus really, so that we can focus all of our energies on the act of prayer and not be distracted even by keeping track of the prayers themselves, so that the prayer is 100% devoted to contemplation of God.
It takes practice and no one says the rosary like that the first time through. But that’s the goal to strive for.
So in answer to your questions: Yes, you can say some prayers without thinking about them and without it meaning anything and I’m sure plenty of people do that sometimes. I know I’ve been guilty more than once of “coasting” through a mass, reciting the Gloria or the entire nicene creed without thinking about it (especially when I was younger). It’s like when you drive home from work, you get out of the car in your garage and you suddenly realize that you can’t remember a single moment from the drive home, like you were sleep walking through the whole thing.
But that’s not what it should be. We have rote prayers for different reasons. Some of the are medititative like the Rosary. Others are meant to be said by the congregation in unity at a mass (and therefore we all have to say the same thing). Some are intended to serve as models for prayer that teach us how to pray like the Our Father. But Catholics can pray freeform too and we frequently do. Prayer is any time when we speak directly to God and offer him our thanks, glorify him or petition him for aid. And how we choose do that is unimportant so long as we do so with reverence, respect, sincerity, devotion, honesty and love.