[quote=@Webmaster]
<Snipped quote by The World>

You could just be repelled by empty space, preventing you from entering any of them.
[/quote]

I think I could make that work actually. Maybe an experiment to tap into the power of the Outside fundamentally changed the experimenter from the other Plane, causing the effect you describe and forcing them to, effectively, watch existences from the vast emptiness of the Outside. And the recording could be out of boredom or some such as, while they themselves can't interact with realities, maybe whatever instruments they use can.

EDIT: Like a sort of trade off. They get the ridiculous power they craved, at the cost of being isolated-for the most part-for all eternity.