From Hebrews 10:1, 4, and 1 Corinthians 5:7
In regard to the verses you quoted, they do not use the word "only". God's holy days are foreshadows of what is to come, so we should live in a way that testifies about what is to come by continuing to observe them rather than a way that denies the truth of what is to come by refusing to observe them. For example, in 1 Corinthians 5:6-8, Paul spoke in regard to how Passover foreshadowed Christ by drawing the connection of him being our Passover Lamb, however, instead of concluding that we no longer need to bother observing Passover, he concluded by saying that we should therefore continue to observe it.
I take it you are not a Christian.