Take for instance the Feast of Tabernacles. To observe it would require an annual trip to Jerusalem, and meeting a long list of requirements that wouldn't be practical for most Christians in the world. There wouldn't likely be enough tree branches for everyone to make and dwell in stick huts. The feast calls for sacrifices by fire. That hasn't been done even by Jews during the past two millennia. In it's heyday God rejected their offerings anyway through prophecies due to the spiritual adultery of Israel.
The benefit was to and for Israel in remembrance of how God provided for the Hebrews during the exodus from Egypt, and provides celebration of the future dwelling of men and God, which was available when Jesus entered Jerusalem on the donkey. The spiritual adultery continued on, resulting in the Jews rejecting that longed-for relationship that is now make for us who believe on Jesus our Christ, having the Lord indwelling us by his holy spirit. It isn't necessary to go seek him out in Jerusalem.
The benefit was to and for Israel in remembrance of how God provided for the Hebrews during the exodus from Egypt, and provides celebration of the future dwelling of men and God, which was available when Jesus entered Jerusalem on the donkey. The spiritual adultery continued on, resulting in the Jews rejecting that longed-for relationship that is now make for us who believe on Jesus our Christ, having the Lord indwelling us by his holy spirit. It isn't necessary to go seek him out in Jerusalem.
When the day comes for Jesus to rule and reign on the earth, He will fulfill the Feast of Tabernacles. Here's a chart you might find useful. The last 3 are a future event, still to be fulfilled at Jesus' return.
![chart_feasts_0416-1.jpg](/data/attachments/88/88714-40679d906ec822b6af33fd6e0f8d8bd9.jpg)
If someone wants to celebrate the feasts, it's a good thing. It's either looking back to what Jesus has done or it's looking forward to the three that haven't been fulfilled yet.
Like when we take communion with the bread and the wine, we're looking back at Jesus redeeming us from the death of our sins being the Passover Lamb who died for us and forgave us our sins. Baptism does the same, we look back at the death, burial and resurrection of Jesus and do it symbolically as if we died with Him 2000 years ago and were buried with Him and resurrected with Him.
So if one celebrates the Feasts in that way it's a good thing.