The answer to this question depends on many factors.
First, if you are young in the faith or newly interested in biblical creation, you might suddenly realize that your church is teaching serious error regarding origins, such as theistic evolution. This could mean that its theology is skewed in other related areas, such as original sin and the necessity of God’s grace. You should strongly consider finding a church that is committed to teaching the entirety of Scripture.
If your church is unwilling to take a stand on creation, you should be concerned. But consider the reasons before taking action; you may have more than one option.
Some church leaders view young-earth creationism as divisive or think allowing a multitude of views is charitable or scholarly. Perhaps they have not considered the implications the doctrine of creation has on other major doctrines, such as man’s sin, Christ’s atonement (Romans 5:12–21; 1 Corinthians 15:22), or the coming new creation (Matthew 19:28). Some might be convinced with the careful presentation of new information, whether you share books like Coming to Grips with Genesis or meet privately for discussion.
Others adopt compromise views for pragmatic reasons—to offer a wider appeal. They may reconsider if they recognize the long-term harm that comes from compromise, or if they hear deep concerns from those in the congregation who consider young-earth creation a vital doctrine.
If your church is officially committed to young-earth creation in its doctrinal statement but allows members or even teachers to promote other views, this may evidence theological drift, and at the very least shows a lack of doctrinal integrity (Titus 2:7). In this case church members have an obligation to seek out more information.
Above all, make sure your understanding of creation does not become a source of sinful pride (Philippians 2:3). As you make your decision, carefully guard your attitude and actions (1 Timothy 4:16). Would leaving split the church or cause unnecessary strife? Would you leave a void in a vital ministry? If you were to stay, would you be able to comfortably believe and proclaim all that you understand to be true regarding biblical creation?
Ultimately, you will have to weigh the severity of the situation against your ability to submit to the leadership, serve the congregation, and honor God, along with other important factors. Certainly a faithful church member may help strengthen a church’s position on creation.
Given the importance of establishing a right view of God in our evolution-steeped world, it is difficult to see how to justify attending a church that is not committed to biblical creation or does not at least encourage its members to hold and proclaim that view openly. If you face this decision, perhaps the Lord will use you to effect change in your church through godly and humble communication with church leaders, even if He ultimately uses disagreement over this doctrine to lead you to a congregation that is more fully committed to proclaiming “the whole counsel of God” (Acts 20:27).