DE said they wouldn't be balancing around SP long ago when Steel Path was meant to be just a fun mode for the hardcore players. That went out the window with the advent of Incarnon genesis weapons and primary/secondary arcane adapters being largely locked behind the Steel Path.
But, even ignoring that, the original statement was in the context of weapon/warframe stat balancing, not Riven disposition. Also, you can take Incarnon genesis weapons into any mission, they're not limited to Steel Path and are only acquirable there.
I would say -Zoom is harmless, even on Incarnons. Headshots aren't that hard to get, you can do it with hip fire. Heck, most of the time -Zoom is a benefit unless you're trying to fight at really large distances in the open world or something, but that's a highly specific scenario that you don't have to engage with.
If a Riven has 'perfect' stats (aka 3 of the best stats and 1 negative that doesn't matter for the weapon or can even be a bonus like -zoom) it is naturally very valuable. However, this value of course depends on the weapon it is for, with more meta weapons making it a more valuable riven.
The Riven's value decreases significantly if you don't have perfect stats, and the farther you are from perfect stats the worse value it becomes exponentially (it is very easy to roll at least 1 good stat).
DE said they wouldn't be balancing around SP long ago when Steel Path was meant to be just a fun mode for the hardcore players. That went out the window with the advent of Incarnon genesis weapons and primary/secondary arcane adapters being largely locked behind the Steel Path.
But, even ignoring that, the original statement was in the context of weapon/warframe stat balancing, not Riven disposition. Also, you can take Incarnon genesis weapons into any mission, they're not limited to Steel Path and are only acquirable there.