That's what it really comes down to, but I don't think you can draw such clear denominational lines, for there are those within all denominations who are true believers and those who are just nominal believers, which is the same as being not a believer at all I think. And then there are the ignorant, those who believe, but really don't know what it is they believe because they have failed to study the scriptures. Still, I believe a greater responsibility will fall on the shepherds who fail to tend the flock in accordance with God's word.
"Study to show thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. " (2 Tim. 2:15)
"Woe to the shepherds who are destroying and scattering the sheep of My pasture!" declares the LORD. Therefore thus says the LORD God of Israel concerning the shepherds who are tending My people: "You have scattered My flock and driven them away, and have not attended to them; behold, I am about to attend to you for the evil of your deeds," declares the LORD. (Jer. 23:1-2)
Absolutely. And those that are true believers have a responsibility to make sure that they, their families, and their friends are not fed error. If the church will not change or the leadership will not listen, it is their responsibility to leave.