Why should I consider unfalsifiable metaphysics to be in the domain of science at all, rather than the domain of religious speculation?
Today's 'unfalsifiable metaphysics' is tomorrow's Physics.
Neil deGrass Tyson makes a compelling point[0] that:
"But a careful reading of older texts, particularly those concerned with the universe itself, shows that the authors invoke divinity only when they reach the boundaries of their understanding. They appeal to a higher power only when staring into the ocean of their own ignorance".
He then goes on to show examples where Greats such as Newton proclaim some aspect of their work as only knowable by God, but then those same issues are tackled later by people who are unsatisfied by God as an explanation.
[0] http://www.naturalhistorymag.com/universe/211420/the-perimet...