Tell it to DouglasKC, not me. It's his view, not mine.
That's false. The shed blood of Christ can only save.
Jews keep the holy days, albeit differently, than Christians. But this doesn't give them a pass for rejecting the messiah.
However, obedience to the Lord Jesus Christ is deeply tied to salvation:
Heb_5:9 And having been perfected, He became the author of eternal salvation to all who obey Him,
Obedience is spoken of extensively in scripture. The problem with rejecting the holy days and sabbaths of the Lord is that they were given for our benefit...to help us grow spiritually, to let us know the Lord and his great love and mercy. Keeping his days are an expression of love, obedience and joy because we decide that we will sacrifice our thoughts and feelings and let HIS spirit keep HIS days through us.