You don't need to retest everything, you stand on the shoulders of those before you in science. You don't need to redo it, because you know it has been tested multiple times by multiple people and those results have been vetted.
You can even challenge those old findings if you want, and replace them if they prove wrong. Many working theories have been replaced or refined.
I don't think theology and religion are irrational as you seem to suggest, but they are not as objective as science. I would like to hear what you think is an example of religious objectivity. You certainly can't point to a religion based on objectivity, can you? (Unless you lump science as a religion, in which case, ok, fine.)
Nor is science totally objective, but then it becomes sort of a "No true Scotsman" argument if I say non-objective science is not science. There are plenty of theories that are wrong but persist because people won't let go of them.
And it really makes no sense to try and make the Venn Diagram overlap. Science will only work if it is objective as possible, and there is no need for objective knowledge in religion. Ultimately in religion you must believe in something that cannot be measured or proven, and thus is not objective at it's base.
Wave vrs Particle one comes to mind...