Comments of chapter undefined of I Only Wanted A Class In The Apocalypse

I still am a little confused on what blessings are. From what I understand, they are a kind of currency that can be used to gain something like administrator privileges for the system to manipulate it a bit such as making optional quests mandatory. The angels get them after quests in small amounts and humans can also use them to level up in place of a class. But apparently using a blessing instead of a class dooms you to being weak? And blessing are equippable in slots on the status? That makes it seem like blessings are like some kind of passive skill or something. Am I missing something? Do later chapters explain this?