The word “denomination” implies division. Currently, there are over 1,500 divisions in the American Protestant religious landscape. Someone may initially think that choice is good, and in a lot of ways, it is, but is a division in the purpose of God? Jesus prayed, “Neither pray me for these alone, but for them also which shall believe on me through their word; That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me” (John 17:20-21).
Denominations are relatively recent innovations of man. Several hundred years ago, Baptists, Episcopalians, Methodists, Lutherans, Presbyterians, and Pentecostals did not exist. Now, each of them (and more) exist with differing names, doctrines, and purposes. This is not the New Testament pattern. Jesus built one church (Matthew 16:18), and Paul stated that there was only one church (Ephesians 4:4; cp. 1:22-23).
It is necessary to note that there were “denominations” during the days of Jesus. Among the Jews, there were the divisions of the scribes, Pharisees, Zealots, Essenes, Herodians, etc. However, Jesus did not identify Himself with any of them. Certainly, what we refer to as “Protestant denominations” did not exist. They were started in the 1500s.
When we worship God “in spirit and in truth” (John 4:24), we will worship in an appropriate way. The problem is, most denominations add to their worship doctrines that are not found in the Bible: instrumental music, Calvinism, Premillennialism, error on the Holy Spirit, etc. Will God agree with you if you add to His holy word (Deuteronomy 4:2; Revelation 22:18-19)?