my skills have plateaued

Best way to improve is starting to 1v1 through matchmaking.

Other then that, maybe watch a few of goddes 1v1 reviews?

https://www.youtube.com/user/GoddeOfSpring/videos

The AI is quite easy to abuse.

The AI has issues with the following:
- feeding the enemy (throwing away units into the enemy team)
- late game (doesn't build anti-nuke most of the time)
- terraform

There are a few fun strategies that can easily defeat brutal AI. My favourite is just spamming gauss turrets. With the gauss turret blueprint selected, press 'C' to also terraform before you place it, and 'V'/'B' to lower/raise (may have got the hotkeys mixed up). The idea is to raise the gauss so most units can't reach it, the AI does not know what to do with these spiked gauss turrets. Over time, the AI will send units past your gauss turrets, the units will get damaged and try to retreat back. After a while, mix in some desolators. With a few burrowed caretakers, you can use this to farm the AI for metal. This is easiest with the spider constructor.

Using the reclaim, build either paladins or a nuke.

The AI have many weakness, some take skill to exploit and some do not.

1. AI is bad against defenses. Gauss -> Guardian at center of the map can let you gain massive attrition and win from behind

2. Fast high damage units: AI works basically by comparing the unit it has with the unit it can see: if it thinks the force it has is stronger it'd attack, otherwise it'd run away. It doesn't really plan and often slow units are poorly positioned. So you can run fast units and pick off isolated and poorly positioned units and structure, which take reflexes and also judgement on which units you can beat and how to engage.

Cloak and Rover is best for this (glaive/scorcher). The CCR challenge is about beating 2 brutal AI with scorcher on a flat map.

This is a pretty good general skill to have, however the best players generally leave too few units to be picked off and will setup traps with cloaked bombs and likes. Most lesser players can be picked apart with this skill however.

3. Cloaky, vision stuff: if AI can't see your units, it can't respond. Effective Long range units like lance, cloaky units like phantom and general cloaked attack can work very well.

4. Placeholders: the AI don't comprehend placeholders well, you can use it to abuse AI.

5. General Tech: One reason why AI difficulty is inconsistent is because the AI randomly choose factories. If the AI pick a factory where your strategy works against, it may be easy while if it pick another factory it may be hard. Learn unit counters and pay attention to AI factories.

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Finally one can always work on streamlining economy.

quote: press 'C' to also terraform before you place it, and 'V'/'B' to lower/raise

For me it's hold alt and use the scroll wheel, but I'm not sure what is default.
Edit: I just checked the wiki, apparently pressing the 'B' key and changing the height with 'C' and 'V' is the default, apparently alt + scroll has to be enabled in settings for it to work (even though I don't remember ever enabling it)

Select army, press "A" and click behind enemy army. This will initiate an attack move order and your unit AI will kick in, which is much better than what you were doing - suiciding countless units by issuing move orders or direct attack orders on individual units. Notice what your Fencer units are doing, or Impalers.

You had issued 0 reclaim orders. Select a constructor and press "E", drag left mouse button click to issue an area reclaim order. Hold CTRL while starting the drag on a metal wreck and it will tell the constructor to only reclaim metal wrecks in that area.

quote: The AI have many weakness, some take skill to exploit and some do not.

This list misses the most glaring hole:

The (current generation) AI, like the weakest human players, does not comprehend the fact that it *can be attacked*. It plays its opening as if its continued existence and development are guaranteed.

A deep strike force coming at it with high tempo is something that it simply cannot comprehend; it does not see the murder-minded forest in the heavily armed trees.

(It looks like it defends sometimes, but don't be mislead. It's not defending. It just wants to attack your units that are in its vision. It does not attack them for any defensive purpose such as "prevent them from murderizing my base". This means it places zero value on being able to intercept them before they do lasting economical damage)

In 1v1 with a Brutal Circuit, you can win just by walking your commander at it in the first minute and "defending" on the smoking ruins of its base.

Yeah, Brutal AI can be abused with commander pushes like this:
http://zero-k.info/Battles/Detail/1493243?