Don’t worry about what other people are doing with these candles. Here in the US, people use candles for secular reasons, such as on birthday cakes, at restaurants, for decorations (especially at Christmas time), and so on. They are also used in sacred settings such as at church. Just because some people try to use them for evil does not mean that candles are in themselves evil. The same can be said of candles with pictures of Christ, His Mother, and the Saints.
We Catholics are absolute forbidden from trying to manipulate God through practices that are “guaranteed to bring results!” That is considered the realm of the occult, and taking on occult practices is a sin of grave matter.
Does that mean there are NO Catholics who engage in occult practices? Of course not. In any religion, there will be members who through ignorance, defiance, etc., disregard the teachings of their religion to do their own thing – even though they still claim to be members of that religion!
We cannot control what anyone does with a rosary, a crucifix, or a picture of a Saint. If some people use these items for evil, we should pray for them. But that doesn’t make all such items evil.
Thanks for asking such a great question!
God bless you!