No one man directs the workings of our church. If our pastor starts preaching on things outside the Word and the deacons/members vote on it he can be dismissed unlike the Pope.
If I wanted democracy, I'd start a country. If I wanted Truth, I'd build it on a system where the Truth does not change by popular vote.
The heart of the issue, is that you do not trust that the SBC is guided by the Holy Spirit, otherwise, you wouldn't have provisions that allow you to "dismiss" or "leave", as a church. It's similar to a prenuptial agreement. Why bother getting married if you're already prepared for a divorce?
The popular vote as you say is rectified with the Bible, it is the final authority. There is no dissent as long as anything said or taught can be backed up with scripture.
It is not a democracy it is a union of believers that have stock in how they are told to worship when the Bible tells you how, not a man elected by other men.
Christ appointed followers and I do not seem to remember him to have appointed one man as head of the church. He used Peter’s spirituality and faith as an example to form the cornerstone of the church. He started with 12 and then more via the commission and it grew from there.