It's reasonable to assume that if the True and Living Church of God on the earth has been found, then all others would have some degree of apostasy to them, and also not be lead by the living oracles of God.
Either the Church is supposed to be One Lord, One Faith, and One Baptism, in full unity as the Bible teaches, or it is not. If it be not, being something else, then by very definition it cannot be Gods, and it mixes the doctrines of men with the doctrines of God, just as the Bible also teaches. This is not to say there is not God therein, according to the faith of the individuals, and the accuracy of said doctrines and practices. And it is not to say that such individuals are not among Gods children as believers in Christ and righteousness. But, there can be only One Church authorized of God. Even Judaism was in apostasy when Christ came to the earth, and he called the Jews unto them, and chastised them for their "traditions" and having lost the doctrines of God, and there were all kinds of "sects" among them. Yet he still worshiped with them, like we Mormons happily will worship with you, and will only be critical of your traditions, having lost the faith once delivered. But like Jesus, we teach and ask you to come unto the fullness of the Gospel, and His Church, we do not belittle you. There may have been, and may be harsh words at times, but such is not our efforts. We focus on the Gospel, not on your errors, just as Christ and the Apostles did. And also just as the Apostles and Christ, we do not condemn other faiths, instead only teach the Gospel, asking them to come unto Him and the Fullness of His Love.