I do not think that the lower level AIs are really meant to be competitive against humans, as much as provide a tool that humans can use to move up from being a complete beginner to having some finesse under less pressure. As you raise the difficulty of the AI, the pressure will increase.
If we think of the noob range in five levels, the first level would be the complete beginner. This player could easily take a half an hour to leave the Dark Age, may, or may not shepherd, and probably has no idea of how to allocate villagers at appropriate times to necessary resources. Notably, they tend to prioritize berries above other food sources. For this type of player, having a safe space AI is quite helpful, as is the Sun-Tzu campaign’s build order.
A level two player would have experience using, but still be uncomfortable with said build orders, and would be learning about concepts like metas. They would be feeling things out, and have deeply uneven gameplay. They would play against easy, and moderate AIs.
A level three would be what one might call a typical noob, having evened out performance, and even become fairly comfortable with how to perform different aspects of different builds, but working on learning their identity as a player. There are many traps for players at this level, from an obsession with micro over macro, to the inverse obsession with overbooming. They are not be as efficient as more refined players, and oft make the wrong calls, but that is part of learning. A level three noob can handle a hard AI competently. They oft have difficulty against high pressure opponents, but that is part of learning. Level three is a very important developmental phase for a players. They can play successfully on 4v4 Comp Stomps, but if they feel that they are less effective for a task, they need to inform their allies. Most players will be friendly to such players, and provide them with helpful tips, and support in game.
Level four would be the semi-noob, who can be sharply refined on some points of the game, but are once again off-balance. They are more comfortable with building under pressure, and even countering it with some of their own. These players will often choose to play a large assortment of civilizations, strengthening their overall gameplay. They have established preferred strategies and tactics, which they can employ, but try other things. They are common players in 4v4 comp stomps, and perform.
Level fives can beat Hardest/Extreme AIs at a reasonable rate on their own, but consistency will vary, particularly given their civilizations. The existence of this slate is a bit artificial, as they could easily be non-noobs by other definitions.