Under LDS teaching they have a living prophet. This means that the prophet who changed the earthly law of polygamy in order to gain statehood was behaving within the bonds of his office. LDS does not claim there will be no further revelation after Jesus Christ. How could they when Joseph Smith provided a new revelation and restored the Church ( this is their teaching not mine).
FLDS are like the Sedavacanits who claim to be Catholic. They can say what they want but neither history or their Church teaching supports their claims.
After reading the Declaration; one sees that the Living Prophet® didn't even do that.
He left it up to others to figger it out!
Some 'leader'!!