system
Given the following post, respond as if you're commenting on Reddit:
human
[Stargate SG-1] Why do we never see a Goa'uld controlled planed with the AG-3 satellite system?

Daniel Jackson is given a vision of what would happen if he had the genetic knowledge of the Goa'uld.

In it, we see that in the span of a couple of years using earth's relatively primitive technology he was able to build and set up a network of AG-3 satellites that are able to destroy *any* approaching mothership as well as do pinpoint accurate strike on the planet able to vaporise major cities in seconds. In effect given him perfect control and hegemony over earth.

The clear message of the vision is that while powerful the Goa'uld knowledge is inherently corrupting turning one of the most empathic figures into a tyrant in the span of a couple of years.

The issue is though, that a Goa'uld wouldn't have such a problem, and slave labour makes things cheap, so why exactly don't we see any Goa'uld-controlled planet have such a satellite defence system? Especially since it can also be used for strikes against the planet itself giving easy control over the populace as well as an option to fight enemy Jaffa incursions.

I don't buy the 'it's not a real technological possibility it was just a vision' explanation since Shifu was an honest child that wanted to teach Daniel a true lesson and lying about the technology possible would go against that.
gpt
I think there's four aspects here.

First, Daniel is a genius. He and Carter between them make up probably two of the sharpest minds on the planet. That combined with the knowledge of the Goa'uld, without the controlling impact of a Goa'uld mind, has enormous potential.

Secondly, it isn't just any Goa'uld knowledge - Jackson got this knowledge from the harcesis, who by his very nature is considered a threat by the Goa'uld because of the fact that it combines the knowledge and genetic memory of two bloodlines. The last harcesis born, in the 1930s, was killed instantly by Ra to prevent such a threat arising. That amalgamated knowledge is greater than any individual Goa'uld's power, excepting Anubis.

Thirdly, Daniel is motivated by more than the usual Goa'uld motivations of power, domination, and ego. Daniel lost the love of his life to the Goa'uld, and his hatred and determination to defeat them gives him a focus that they lack. They're usually focused on political maneuvering, and on oppressing less advanced species into a chattel race, not on actively standing up to an equal or more powerful race. His motivations to defeat the System Lords and protect Earth from them focuses all that knowledge in a way that the Goa'uld don't typically have. Remember, until Earth's first proper Stargate mission in the 90s, when Jackson himself first decoded the gate, the System Lords were united under Ra's rule. There was very little infighting. Their only major enemies were the weaker races they enslaved. 

Lastly, in the Stargate Universe, Humanity is Special. Within a few years of gaining access to advanced scientific ideas through the gate, they're able to develop technologies that should otherwise have taken centuries to invent. They carry within them the potential to succeed the Ancients, and even to ascend. The Tau'ri of Earth show not only intelligence and determination, but *creativity*, creativity that the Goa'uld lack, thanks to millennia as a stagnant and arrogant society, dependent on slavery and utterly convinced of their own superiority. The Humans' ability to think creatively and to come up with clever and unexpected solutions is ultimately what defeats the System Lords, turning the tide of a struggle the Tok'ra had been limping through for centuries - and Daniel represents some of the best of that ability. That creativity, combined with the amalgamated knowledge of the harcesis child, leads to new innovations, something the Goa'uld haven't had for centuries, and only really ever seemed to have under Anubis and Ba'al.