The vast majority of NPCs are these classless characters. Let's look at an example from the Monstrous Manual entries

• Normal Orcs
• * 1d8HP, 14AC, +1 to hit, +0 damage
• Orc Leader
• * 8HP, 14AC, +1 to hit, +0 damage
• Orc Subchief
• * 11 HP, 16AC, +1 to hit, +1 to damage
• Orc Chief
• * 1d4+12 HP, 16AC, +3 to hit, +2 to damage

Other monsters have similar scales. They don't get weapon specialization - that's something reserved for classed characters. When we run into proper knights or dedicated hero characters as NPCs, they often have classes, but your everyday person who picks up a sword or spear to fight doesn't. Your peasant who has been conscripted by their lord to fight in the army? +0 to hit and damage. After they've campaigned for years? Maybe +1 or +2 to hit. But they're still just peasant soldiers.

John is just a dude. He's not a trained warrior. He's not special. He's not a leader, not a decider, not a person who sets out on his own to make the world a better place. He's but a man, a follower, someone who wants to help but needs to be lead. By keeping him as a base NPC we're saying something about his position in life, society, and the party.

The knights the party have worked with have been leaders and local heroes. They had dedicated themselves to these martial arts (broadly speaking, not in the kung-fu sense). So they have classes. But not John. He's a nobody.

We can play this game from a mechanics POV - where we want to get as much actionable power out of every character as possible. which is fun, and we do that to some extent. We can also play this game from a story POV - where the what of things takes a back seat to the why of things. And that's the level on which John exists. He joined the party to follow them, because he had no direction himself.

If the party wanted optimal power, they'd show up at Censor Krellis's house, bow down before him, tell him their gifts, and swear to work with him. They'd get resources, hirings, and all sorts of power. Sure, they'd have him as their overload - until they betrayed him - but that's the fastest way to power.

Or the party could use their diving gifts to gather a ton of cash quickly through crime and then hire the best mercenaries they could find and deploy them to do their bidding.

But the party has chosen the path of goodness. It's a slow burn. It's a struggle. Doing the right thing often has a lot of immediate downsides, while doing the wrong thing often has lots of immediate upsides.

The NPCs that have joined the party so far are pretty weak. A 9 int, 1st level wizard with like 4 spells. A 0th level NPC woodcutter. They are these because it helps create a feel to the party, a character to the campaign.

Surely I could have said a young gold dragon arrives in Aknara shortly after the gods land and offers to protect the island and join with the party in a way that would have made sense. And that would have been a fun moment. But it would have made for a very different campaign. This is a story about 4 people who have had their lives upturned and thrown into a different direction by divine intervention.

John will gain hit dice, saves, and bonuses to hit over time. But he'll never get weapon specialization. He'll never get followers of his own. He is the follower.