Joseph Smith: I told the brethren that the Book of Mormon was the most correct of any book on earth, and the keystone of our religion, and a man would get nearer to God by abiding by its precepts, than by any other book. – History of the Church, 4:461
People today: Except this part as it doesn’t apply to us, and except that part also, and don’t forget to exempt this other part as well.
Joseph Smith: If any man preaches to you, doctrines contrary to the Bible, the Book of Mormon, or the Book of Doctrine & Covenants, set him down as an imposter…Try them by the principles contained in the acknowledged word of God; if they preach, or teach, or practice contrary to that, disfellowship them; cut them off from among you as useless and dangerous branches. – Times & Seasons, vol 5, pg 490
People today: We have modern prophets who received revelation that tell us we don’t need that anymore.
Joseph Smith: There have also been ministering angels in the church which were of Satan appearing as an angel of light:— A sister in the State of New York had a vision who said it was told her that if she would go to a certain place in the woods an angel would appear to her,— she went at the appointed time and saw a glorious personage descending arrayed in white … he commenced and told her to fear God and said that her husband was called to do great things, but that he must not go more than one hundred miles from home or he would not return; whereas God had called him to go to the ends of the earth; and he has since been more than one thousand miles from home, and is yet alive. Many true things were spoken by this personage and many things that were false. – How it may be asked was this known to be a bad angel? … by his contradicting a former revelation. – Times and Seasons 3 [April 1, 1842]: 747
People today: We depend on the prophets and leaders to tell us what to worry about.
Joseph Smith: President Joseph Smith read the 14th chapter of Ezekiel [see, for example, verses 9-10: ‘If the prophet be deceived when he hath spoken a thing…the punishment of the prophet shall be even as the punishment of him that seeketh unto him.’]…said the Lord had declared by the Prophet [Ezekiel], that the people should each one stand for himself, and depend on no man or men in that state of corruption of the Jewish church — that righteous persons could only deliver their own souls — applied it to the present state  of the Church of Jesus Christ of Latter-day Saints — said if the people departed from the Lord, they must fall — that they were depending on the Prophet, hence were darkened in their minds, in consequence of neglecting the duties devolving upon themselves… – Teachings of the Prophet Joseph Smith pp. 237-38
People today: We are taught we don’t need to worry about these mysteries.
Joseph Smith: I advise all to go on to perfection, and search deeper and deeper into the mysteries of Godliness. – TPJS, pg 364
To the last quote: People today would say that we don’t need to worry about those things as it doesn’t affect our eternal salvation.
But they would be wrong.
If we don’t continue in seeking we loose what we currently have to the point of damnation.
9 And now Alma began to expound these things unto him, saying: It is given unto many to know the mysteries of God; nevertheless they are laid under a strict command that they shall not impart only according to the portion of his word which he doth grant unto the children of men, according to the heed and diligence which they give unto him.
10 And therefore, he that will harden his heart, the same receiveth the lesser portion of the word; and he that will not harden his heart, to him is given the greater portion of the word, until it is given unto him to know the mysteries of God until he know them in full.
11 And they that will harden their hearts, to them is given the lesser portion of the word until they know nothing concerning his mysteries; and then they are taken captive by the devil, and led by his will down to destruction. Now this is what is meant by the chains of hell.