You are plainly incorrect. The "holy days" were added in the same context as the sacrifices. There is no biblical reason to divide the cultic law that was given to Israel through Moses over a relatively short period of time. It's an arbitrary decision on your part in order to make some theological point.
The fact remains that the "holy days" were part and parcel with the Levitical system. E.g., the are given their fullest expression in the book of Leviticus. Any attempt to bring them into the new covenant, even in an expurgated form, is a denial of the finish work of Jesus Christ on the cross.
Exodus 12:14-16, "This is a day you are to commemorate; for the generations to come you shall celebrate it as a festival to the Lord-a lasting ordinance. For seven days you are to eat bread made without yeast. On the first day remove the yeast from your houses, for whoever eats anything with yeast in it from the first day through the seventh day must be cut off from Israel. On the first day hold a sacred assembly, and another one on the seventh day. Do no work at all on these days except to prepare food for everyone to eat-that is all you may do."
Later on in verse 29 the Lord struck down all the first born in Egypt. In verse 51 all the Israelites were brought out of Egypt by their divisions.
It wasn't until a year later that the sacrificial system was instituted (Galatians 3:19). It was added because of transgressions until the Seed to whom the promise referred had come.
The fact remains that the "holy days" were part and parcel with the Levitical system
I was quoting Exodus....and now I will quote Mark. "These people honor me with their lips, but their hearts are far from me. They worship me in vain; their teachings are but rules taught by men. You have let go of the commands of God and are holding on to the traditions of men." (7:6-8)