Why doesn't the church keep the Biblical Feasts?

First to star off, this is sort of like a few questions in one, so I want to apologize for the length. I also should probably state that I am a Catholic, but have always been very interested in Scripture, Church history etc…
Now then, why doesn’t the church keep the biblical feasts? I understand that Easter and Christmas are important because of what they signify, but nowhere in the Bible does it say to keep them. Also, I know that the church calendar is heavily based around the date of easter, but I don’t know how the actual date of easter was figured out, only that it had to do something with Gregory the Great, a la the Gregorian calendar. Also I read somewhere that the Jewish people modified the dates according to rabbinical tradition after 70 when the Second temple was destroyed. Therefore, technically, the feasts in the bible, as I see them are not just Jewish. Even the name “Jew” doesn’t even occur in the Bible until 2 Kings 16:6. Also Leviticus 23:2, God says “these are my feasts”, not necessarily Jewish ones. I don’t know about Easter, but I also know that Christmas was not even that big of a deal in the early development of Christianity and to this day, there is a lot of controversy I get every year from non - Catholics about celebrating Christmas.
Again, sorry for the long worded message but any help would be appreciated!
Thanks and God be with you

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