I gather that our own dear C of E is contemplating changing the service of Baptism because no one understands it.
Where on earth does one begin with this?
My children were baptised RC. The church insisted that parents attend a short course explaining what it was about. Problem solved. And if one doesn't understand absolutely everything, does that even matter. Take it on Faith. Accept that some things are unfathomable mysteries. Or, if you must, just sit there nodding politely until it's all over as many generations have done already.
Or, use your brain. Ask yourself this: "Why am I getting this child baptised? I have no idea what Baptism is or what the service means. I can't be bothered to find out, so the logical thing to do is not to go through with it."
Clearly, if you have a congregation who by and large never darken the church's doors, they are not going to understand what's going on. Funnily enough, the church managed to survive for centuries, despite the service being conducted in Latin. People just got on with it. I realise that a Christian priest finds it hard to say "that's their problem if they can't be bothered", but I would also suggest that it's not something that's going to be resolved by changing the words a bit. Or a lot. And undoubtedly for the worse (for an illustration of what I mean, compare the Book of Common Prayer version of the Catechism with the latest milk and water version).
People's brains have not, by and large, got any smaller since the Middle Ages. If they wanted to understand the Baptism, they would. If they don't, it's because they're not interested. And by making the service 'modern' and 'understandable', you will make it less interesting. Paradoxically, making the problem worse. Which is just one of many reasons why the Church has become less and less loved as it has become more and more 'relevant'.
I'm no expert on Islam, but they seem to do all right with scriptures written in classical Arabic, a minority language even in the Muslim world. That's because they have faith. If you don't have faith, you're not doing to understand Baptism, even if the service is written in Janet and John. Get over it, move on and love God.