It is never wise to make sweeping generalizations, particularly when it comes to matters of salvation. As Christians, we are not called to determine who is among the elect—that is God’s domain. While many Seventh-day Adventists are genuine, born-again Christians, this is in spite of official SDA doctrine, not because of it.
There are individuals within Seventh-day Adventism who do not adhere to the problematic teachings of the organization. However, it is important to recognize that the official teachings of the SDA Church teach a false gospel (Galatians 1:6-9) and promote a false god (2 Corinthians 11:1-4), neither of which can save someone. This places the organizational teachings outside the bounds of Christian orthodoxy. As a result, born-again Christians should not align themselves with a church that teaches damnable heresy.
Instead, Christians should always be ready to share the true Gospel of Jesus Christ with those in the Seventh-day Adventist Church, just as we are called to do with all peoples, tribes, tongues, and nations.