They are implementing things as they learn about them. They got information on Sting when Sting was used against the necklace, same as a lot of their detection methods. With Vista's shard, they learned how to expand and contract space. They can't do it the way Vista did it, because they don't have a vast reserve (like an entire other Earth, perhaps?) to add air when expanding space, or store air when contracting it. However, they are using the information to improve their portals, and they can both sense and communicate longer distances with the Vista data.
In fact, the only one shard that didn't give something broadly useful was Bakuda's shard, and even then it gave hints on the mass-to-mana conversion needed for the solar system scanning spell. Sophia gave them an entire new set of dimensions to play with, even if they don't play well with mana. Vista gave the aforementioned communication and portals upgrade, and QA gave the Multitasking and Bug Control systems, the former of which is half the reason they were able to progress as fast in rebuilding their magic system.
I'd argue that kinda proves my point:
Bakuda somehow made awesome stuff with methods that were unsafe. However, the world did not implode, so safe
enough could potentially be argued. Taylor still has no bombs that clean up the boat graveyard in one octarine flash.
She absorbed Vista's power, and yet can't expand space even with access to other dimensions/planets for air (just like the Shards do)
and enough of a hyperspace arsenal to store
multiple Shards being digested.
They can't reuse Stalker's power because it disagrees with magic. But they HAVE Shards to run it on. Still, this one may have the best reason: it probably disagrees with the magic in her brain, and I'd have moral qualms about being gasified and having what's
possibly my original consciousness simulated for the duration.
And then there's Sting, which they can use exactly like the original owner (while using magic to apply it and create projectiles,
even if it doesn't directly work on mana itself) without having eaten that Shard.
In addition to what others have mentioned, how would you make a poison be able to propagate itself through living, crystalline, massive life forms in such a way that not only does it keep that one shard from simply splitting off the poisoned part to protect itself, but also sends that poison on to the other billion shards that make up the Zion entity? Wildbow went crazy with overdoing things, but even if the size of individual shards wasn't prohibitvely large, the fact that Zion and Eden are colony organisms, that is, life made up of many independently functioning life forms that make a cohesive whole, means that the most likely natural response to a poison is to shed the poisoned member of the colony, and thus preserve the whole.
To be fair, you have a point. However, there's also this really cool bit of nanotech that suborns a being's native machinery to mindlessly make copies of itself before it self-destructs, releasing its payload to subvert other systems. It's called the Flu.
Admittedly, it's a fair chance that they have already encountered something similar, so they may have an immune system, but viruses are always more effective than a poison.
