I have been wondering this as some of the threads, and people I meet on the highways and byways. Isreal as a nation was from the Mosaic law and ceremonial law from the exodus on. Abraham, Melchizedek, Job, Isaac, and Jacob, Adam, Eve, Noah, Enoch where not Hebrew, in that sense. They lived out the revelation that God had given them at that time.
Israel was to prefigure Christ's coming, etc, but Christ is here, do we need to emulate life prior to Christ in order to know Him, or are we filled with the Holy Spirit who teaches us all things?
Col 2:16
Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day.
If they want to celebrate that, have at it.
It seems however that it can lead to an elitism attitude, like they really know what it's all about from special information or something. I am not saying this is the case at all times, but it's definitely a possibility.
I went to a messianic service, and the pastor completely ignored me, but conversed with my friends who had Jewish backgrounds. He knew them, but I was completely new, and he didn't know if I was saved or not.
Is living in light of the revelation of the Holy Spirit, the inner man, so hard that we think if we do these Sabbaths and feasts etc we will know what the Holy Spirit cannot teach? Is that looking for a spiritual experience that fades away a day or two after the festival, or looking for the living active presence of the Holy Spirit who helps us worship in spirit and in truth as much as/as often as we desire?