...it's worth noting that enemies in 5e aren't built like players...
That's a crappy system. NPCs with class levels should be built just like player characters.
If the scene needs to the NPC to be stronger, raise the level.
And I totally think crafting every NPC in BG3 using PC character creation would be a nightmare.
Larian has how many employees?
30 NPCs? That's not even an afternoon's work for one person. If I had an employee who was that unproductive, said employee would not last long.