What follows is my personal opinion1:
In 1 Corinthians 1:10-17, Paul warns the Corinthians of the dangers of splitting into factions; which are the seeds of denominational splits. See especially verses 11-13:
My brothers and sisters, some from Chloe’s household have informed me that there are quarrels among you. What I mean is this: one of you says, ‘I follow Paul’; another, ‘I follow Apollos’; another, ‘I follow Cephas’; still another, ‘I follow Christ.’ Is Christ divided? Was Paul crucified for you? Were you baptised in the name of Paul?
This is the negative effect that we often think of when we think of denominations. However, Paul's letter later highlights something which could show denominations as being part of God's plan. 1 Corinthians 9:19-23:
Though I am free and belong to no one, I have made myself a slave to everyone, to win as many as possible. To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. To those not having the law I became like one not having the law (though I am not free from God’s law but am under Christ’s law), so as to win those not having the law. To the weak I became weak, to win the weak. I have become all things to all people so that by all possible means I might save some. I do all this for the sake of the gospel, that I may share in its blessings.
In other words, Paul becomes whatever is necessary to enable people to come to Christ and to avoid being a stumbling-block to anyone wanting to come close to God.
So, if someone likes formal music and a liturgy, God has provided a denomination for them. If someone is looking for a more informal setting, or a church with a bias towards the poor, or a church which baptises with lots of water, or not much, or a church which is broad enough to include all these, there is a denomination for them. The human part of the church is flexible so that people can always find God in a community of believers.
I'm also focusing on mainstream (for want of a better word) churches / denominations.