Why do 7th Day Adventist reject Jesus teaching about the unnecessary obligations Sabbath?

First, the only Sabbath is the one GOD himself put forth in the Ten Commandments. Second, the real reason Sunday worship came about was because of the RCC. Christ couldn't have risen on a Sunday - the timing would not be correct - for all the spouting of those who claim they know. Sunday is NOT the day that Christ taught to follow - only the RCC did that.