People just presume there exists a reality that is the cause of the subjective experience. They go forth and act according to that presumption.
Scientific methodology tries to limit reliance on subjective experience, though in reality that is all there is. Still relying on multiple sources provide a greater confidence in a reality behind the experience. Test and validate through as many sources as possible. At lest until you feel confident in the truth.
Problem with God is a lack of ability to validate the claims consistently. With science, if even one validation fails then the reality of the claim is immediately suspect.
With religion, it is the faith of the believer which is suspect. Not the reality of the claim. If you have "enough faith" then the reality of God would become apparent. So you can't rely on your subjective experience unless of course it supports the belief. Discount every experience which fails to validate your belief as a lack of faith.
It kind of does, to that person. We individually decide what to accept as truth and it becomes our reality.
There is your truth, my truth and the truth we share. We all presumably determine this the best we can but there are no guarantees about the realities behind the truths we accept.