The principles that have been discovered by the church growth movement are helpful and important. The methods that have been devised to help us take advantage of those principles are valuable. And the people who promote those principles and methods are doing their best to help churches and ministries.
In short, the majority of church growth material is great.
But it’s not fool-proof. There are no guarantees.
Except one. The one given by Jesus that he would build his church.
But Jesus never promised relentless, unceasing, inevitable numerical growth for any congregation. Not even for the faithful ones, (as we see in the struggling, faithful congregations in the New Testament).