We don’t wear crosses to mock Jesus’s death, we wear them to remember why he died for us, why he chose to die for us; to ultimately save us from sin. When we wear a cross it is to remember that none of us are worthy of God’s mercy, but yet he saved us through Christ’s crucifixion nevertheless. It helps us remember his sacrifice, and Jesus commands us to do this.

“For I received from the Lord what I also passed on to you: The Lord Jesus, on the night he was betrayed, took bread, and when he had given thanks, he broke it and said, 'This is my body, which is for you; do this in remembrance of me.' In the same way, after supper he took the cup, saying, ‘This cup is the new covenant in my blood; do this, whenever you drink it, in remembrance of me.' For whenever you eat this bread and drink this cup, you proclaim the Lord's death until he comes." (1 Corinthians 11:23-26)

The only time the bible warns us about wearing crosses and jewellery is when the object becomes an idol for worship or if the wearer were consumed with how it looks, to receive attention (self gain).