This was certainly my initial thoughts when reading that specific passage.
Jesus was put to death “but made alive in the spiritual realm” and “In that state He also went and made a proclamation to the spirits in prison”.
I find it odd that this pastor is using this to justify his own practices because what Jesus did here was very specific to his own fulfilment of death and resurrection. Even if we struggle to understand exactly what it means that he preached to the spiritual realm, I’d say this passage is not prescriptive for Christians to follow because it seems to be a very unique action that Christ fulfilled in that moment, as he proclaimed to all heaven and earth that death has no power over him.
Preaching the gospel to spirits of those who are deceased calls into question the whole idea of whether we have eternal opportunity to accept the gospel once we have died, and therefore is the gospel really needed if spirits can choose heaven in the afterlife?