Is it vain? Worshipping God in a denomination?

Yes, it is in vain, and empty worship. Worshipping God must be in spirit, and truth.  John 4:24

Being in the spirit is having the holy spirit, the holy spirit

is given to those who obey the gospel of Jesus Christ Acts 5:32.

ARE YOU IN THE CHURCH OF GOD, THE CHURCH OF CHRIST?, OR THE SYNAGOGUE OF satan?

Is the church you are a member scripturally organized?

Mat 15:9  But in vain they do worship me, teaching for doctrines the commandments of men.

Mrk 7:7  Howbeit in vain do they worship me, teaching for doctrines the commandments of men.