system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40k] if rowboat girlyman happened to find a STC, would humanity have a serious chance at overcoming the threats around them ?.

Let’s good old robot grindman found an intact stc on a planet, and knowing what it is, immediately started using it to better our technological capabilities and reform the mechanicum. How would things play out ?.
gpt
Assuming that it's fully functional and **uncorrupted**, it would be the find of the century. It would likely be years or decades before anyone would feel the impact, though. The tech that would be 'ready to go' right out the box (like incremental upgrades to currently-extant weaponry and equipment) would need to be disseminated, and factories currently producing the old models would need to be systematically upgraded to the new ones, in a staggered fashion to reduce disruptions to the overall supply chain. The more advanced stuff (genuine lost technology) would likely take multiple iterations of building the needed tools/infrastructure so that you're capable of building a new tier of needed tools/infrastructure, which in turn would consume resources not being directed to more conventional weapons/technology. 

And as others have noted, the raw scale of the universe (and of the threats bearing down on the Imperium) means that no individual thing is going to be an "I win" button. Alone, the STC won't save humanity, it would just mean that the humans would take more xenos down with them on the way out.