I am developing a capacitive sensor with my Arduino UNO,
but I am having a problem with low sensitivity.
So you know that the technique you are trying to use is not reliable and repeatable and is not used in any commercial system. It is in the tutorial as a novelty, many people have made the mistake of trying to develop it but unfortunately it is not a good technique to use.
You are free to try however, but this is the sort of problem you run into.