I believe your reasoning is exactly backwards - it's far better (and it is God's plan) that we have His written word and do not need to rely on visions, dreams etc, to know Him and His truth. The only way man can know God and His truth is if God determines to reveal Himself to us - we do not have the capacity to discover or figure God out. Now, there are indeed times and ways that God speaks to us individually, privately, but we need a measure, a guide to examine our visions, dreams, that small voice, etc, to be sure it is God and not our own inclinations or assumptions.
If someone tells me that God has told them 'whatever', how do I know if they are speaking for God or deluded or conniving . . ? . . I have God's own revelation of Himself and His truth, the Bible, to measure any private vision or dream by. If Joseph Smith or Charles Taze Russell or Ellen G. White or whoever tells me that I must join 'their' group, that I must keep 'these' rules, etc, then it doesn't matter what visions or dreams they've had I know what God has revealed to us in His own word and I know these folks are not in accord with revealed truth.
The problem is people don't own an informed understanding of the reliability of Scripture; those who advance that surely the Bible was put together by Constantine for his own best interest and certainly books were left-out and other included by bad guys wanting to control people and even if all started-out well the texts are simply so ancient that of course the Bible we have today has been altered and corrupted, etc, those who assert such notions have gained a hearing even within the church. Textual criticism and archaeological discoveries simply evidence the opposite - the Bible we have today is an accurate translation of what was originally written.
It simply seems far more sensible to me to place our confidence in God's own authoritative revelation of Himself and His truth than to trust in my own visions and dreams, etc. I published a hub on the Bible addressing this very matter.