That is not what a denomination is. YouR description is more in line with that of a cult. Denominations often have a written confession or statement of faith. Rarely are they governed by one person.
What you write here is basically what I’m talking about. The group who writes that confession or statement of faith is typically the human authority (at least for Mainline Protestant Churches). I was not implying that all are governed by one person, but non-denominational often are or at least have a “Senior Pastor” who has the right to hire / fire other pastors.
Again, I’m not talking about preachers who hide their denomination name/allegiance either, and still abide by Assemblies of God , Southern Baptist, Liberty Baptist, etc.
I’m referring to true, non-denominational who teach what they feel is true based on what they took away from their individual training and schooling (if they even had formal schooling).
In my view (and the view of everyone who says there are tens of thousands of protestant denominations), each “non-denominational” is their own denomination.
The fact that some “non-denominational” churches start setting up satellite locations is proof of this. They essentially are new denominations that currently only have 1, 2 or 3 Churches. The question becomes how much do they intend on growing in the future, and how do they plan to continue after the retirement/death of the Sr. Pastor?
But again, the argument is that they are each their own denomination.
So again, ignore mainline protestants. The non-denominational Church is what we are referring to. And the confessions or statements of faith that typically use are so generic. They simply state that they are sola scriptura and the bare minimum to be consider a Christian. Those confessions / statements of faith never go into true theology.
God bless