Scripture, the word of God, is what I base my beliefs on. I think there have always been Christians that have observed the feast days that Christ created, but they have been persecuted, marginalized, and shouted down throughout history.
Here's an idea: go do Christ's work. Counsel single mothers, protest at an abortion clinic, pray for others, fast, give to charity. Instead of sitting around selling a gimmick about how bad a holiday Christmas is.
Those are good works. And you don't really know what I do in my personal life.
Joh 6:29 Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent.
When Christ told us to observe his feasts, I believe him.
Pharisees loved scripture alone too, it let them ignore what was clearly the spirit of God so they could profit from legalistic interpretations.