I think a part of Purity is also: they care a lot more about the individual than the other affinities. I mean all of them care about humanity in a big picture way, but Purity cares about living breathing humans in the now.
That's a good reason for why they don't want excessive genetic improvement or excessive automation: it creates inequality, poverty and so forth. If a P/H demigod exists, all living baseline humans are minions. If a P/S factory drone operator can control a small factory single-handedly (still not Supremacy with its autonomous operation), then a legion of exoskeleton-equipped workers just lost their jobs.
Purity is willing to forsake some technology, not just out of fear, but because they are willing to go the slow path with incremental automation, incremental changes, giving everybody a niche they can excel in. That is also evident in their victory: it's about rescuing the current Earthlings, not just about constructing a better future by any means necessary (Supremacy).
I'd give the other affinities the benefit of the doubt and say that they all value human life, though not neccessarilly the human form.
If
everyone receives some basic genetic fixes, everyone is better off - though that would likely be a new generation thing.
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Automation and freeing up labor is a path to greater wealth, not a loss.
It's been the pattern of history for labor-saving inventions to lead to greater wealth and specialization in society, and Purity knows history well.
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Supremacy in a sense has an entirely different version of a bright future, not simply a different way of reaching it.
Purity focuses more on fulfilling human needs while Supremacy focuses on reducing or replacing human needs.
Purity's ideal utopia is one of wealth, leisure, and plenty: Supremacy's utopia is for people to enjoy themselves in a virtual, simulated utopia via uploading or uplinking.
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They are distinct visions, but that doesn't mean it should be impossible for a colony to alter or deviate from those visions, or to create its own vision incorporating some aspects from multiple pure affinities. After all, mixing aspects of the parent affinities is exactly what hybrid affinities are supposed to be about.
It makes perfect sense for a colony to be able to explore multiple low level affinity bonuses, which require a less extreme commitment to their respective affinities. Higher level bonuses become gradually but increasingly difficult to incorporate, to the point where many combinations can't be achieved in anything but extreme sandbox play. I think this "soft" limitation on affinity mixing is thematically appropriate, and it makes for much more interesting gameplay options than an explicit ban on mixing affinity bonuses beyond a certain fixed level.
So is your main concern pure affinities using buildings from other pure affinities? I think it makes sense to allow that for early game buildings, as these buildings haven't yet gone too far down the path of their respective affinities. For later game buildings. Higher level buildings should have high enough affinity prerequisites to prevent use by other affinities even without an explicit restriction.
The more open it is, the more you punish players trying to focus on an affinity and the more you encourage just taking some of everything.
By definition that makes them less distinct mechanically, which conflicts with them being distinct in philosophy.
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The Buildings point could actually be a major problem with pure affinities if Firaxis doesn't make some requiring higher affinity levels.
Currently a single affinity approach unlocks them in the early mid game - meaning that a hybrid affinity will have far more buildings unlocked come late game currently.
In light of the hybrid system and some of the buildings being kind of useless, there needs to be some redesigning.
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@Barathor
I think all of the later level Infantry units look a bit taller, for various reasons.
For Purity, I'm pretty sure it's power armor.
(Though not the walking tank that is the Battlesuit.)
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@Red Menace
Yes, I'd like to see some strong Affinity buildings that really change how the game is played - and ideally make for some interesting tech path choices.
While I don't think it could be balanced without locking players into an affinity or hybrid, unique hybrid affinity buildings could also be fun.
Perhaps at very least they could be unlocked for high-ish hybrid numbers?
They still badly need their own victory conditions.