Reda really is a major problem with this series. He basically has as much knowledge about his world as a fresh transmigrator. Pretty much every character has been shown to be more knowledgeable in basic things about the world than Reda. Reda doesn't really understand the value of using magic or healing skills, doesn't really know the value of being a healer, and doesn't know most people can't learn magic immediately by reading it in a book. He wasn't born knowing healing skills and his job as an adventurer made him travel a lot. Unless you do not interact with the world at all, you should have some understanding of the professions around and the commonality of skills.
Pretty much the only person the story convincingly shows Reda caring about is Mina who he loves like a daughter. Everyone else is on the same level as a friend and to be honest, it's unlikely he actually would differentiate between an acquaintance and a friend so it's not a high bar. The story can't even be bother to show Reda learning about the people around him, let alone show him starting to care about the misfits declaring themselves his wife.