It's ironic that those who would foolishly condemn keeping the biblical festivals are steeped in the whitewashed paganism of the Babylonian Mystery Religion (with its baptized paganism, its hollow daze) and refuse to see anything wrong with their spiritual adultery and idolatry!
"[Paul] warned the brethren not to be intimidated by some who were questioning their manner of keeping God's feasts, as well as the Sabbaths, new moons, and eating and drinking. He said, "So let no one judge [criticize or condemn] you in food or in drink, or regarding a festival or a new moon or sabbaths, which are a shadow of things to come . . . Let no one cheat you of your reward ..." (Colossians 2:16-18).
Paul was combating a group of ascetics who were introducing several strange doctrines, including worshiping angels (verse 18) and abstaining from wholesome food and drink (verse 21). He told the brethren to ignore them and continue observing what he had taught (and he certainly taught keeping the Passover, as we have seen). Regrettably, the Colossian brethren had been cowed by these self-righteous intruders and were starting to shy away from observing these feasts.
So Paul mentions how important they are, as foreshadowing coming events in God's plan for mankind. These events have not been completely accomplished so far, and many are still in the future."
The Biblical Festivals That Teach Us About Jesus Christ
Colossians 2:16-17: Are God's Laws Obsolete?
Colossians 2:16-17 by Larry J. Walker
Colossians 2:16 Shows Gentile Christians Kept the Holy Days