Most everyone on this forum, I believe, are born again, if they are here for the right reason, but look at the many different doctrines represented. They are all God's sheep, born again, and destined for heaven. Jesus said that God has hidden the mystery of the truth of his gospel to many and revealed it to only a few (and that is a big question I have for God "WHY") nevertheless, just because you are following the doctrine as instructed by man, does not mean you have lost your eternal destination.
What I stated was that when the believer follows men (or the doctrines of men), he/she remains as a newborn babe who feeds on the milk of the Word and does not progress to the meatier matters. Scripture indicates that those who follow men or the doctrines of men are carnal, envious, striving, and divisive:
1 Corinthians 3:
1 And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ.
2 I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able.
3 For ye are yet carnal: for whereas there is among you envying, and strife, and divisions, are ye not carnal, and walk as men?
4 For while one saith, I am of Paul; and another, I am of Apollos; are ye not carnal?
In Ephesians 4, we are instructed not to be children so that we are able to discern deceitful doctrines.
Ephesians 4:14 That we henceforth be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive.
We are to grow up in the Lord Jesus Christ so that we effectively work in order to increase and build up the body of Christ in love.
Ephesians 4:15-16 But speaking the truth in love, may grow up into him in all things, which is the head, even Christ: From whom the whole body fitly joined together and compacted by that which every joint supplieth, according to the effectual working in the measure of every part, maketh increase of the body unto the edifying of itself in love.
We will never reach the point of the Eph 4:15-16 believer if we continue to follow men and/or men's doctrines. Following men's doctrines results in the believer being tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive.