Why would they abandon their own design vision because someone else announced a game with a similar - but not identical - mechanic?
It's not that Firaxis would want to abandon their design vision. But it can be imagined it would make things more difficult for them at the ERB meeting with 2K. Someone said it is probably oiled, true, and but there are still questions the suits usually make. As it was commented, if they were taking on an HK failed feature, it would have been difficult to get any approval for it to be included, or a lot of questions about on "How you would ensure it will not fail?". HK having just presented the feature as a big selling point is a different scenario, but also one open to questions, mainly "how will this been as original if someone has presented it already?" "how would you differentiate it?" or just "are you just presenting what Amplitude said yesterday because you have no other ideas?"
i don't how many times this can be repeated
who had the idea first is truly irrelevant to the fact that it played badly in Humankind and it doesn't look to be done in a much better way in Civ VII
You are right in the fact that having the idea first or not has little relevance on how it will be implemented. But having a clear timeline does provides some nuance that invalidates the basic statement "humankind had an idea that proved wrong, THEN firaxis took it for their new game" that seems to be repeated quite a while.
With the timeline presented in the article, the first step of the timeline is "humankind hand an idea that was presented as a big depart from Civ-series, THEN Civ pitched 2K management to include a similar idea in their game": This alone (as commented above) proves they are not the exact "same" idea, as in that case it would probably not been able to make the cut trough 2K Civ7 approval board: Firaxis had probably the need to convince them it would be handled somewat differently to what Amplitude was presenting with Humankind.
Then the second step is (several year laters) "the feature was a failure in humankind, THEN Civ team decided to keep it in their game", which leads to a very different scenario: first Civ'7 feature has already been for a while in development, so dropping it may mean -as core as the game as it is- just re-start a game development from scratch, loosing the work (and money) of several years. Then, humanking failure provides them relevant information on how to tweak and differentiate more their feature to avoid the bigger shortfalls their competitor had (as long as they not are very hardcoded already), or at least to "patch" them for minimal impact. Knowing this "feature coincidence" I'm sure they have had been keeping a look on Humankind and making sure they are able to diffirentiate it so it does not follow the same path. I think it is too early to say the new path will lead to success or failure, but I'm sure it will be a different one for shure.
BTW, I take the opportunity to say: I've played Humankind quite a bit, and I don't find the civ-switching to be one of the worst things in the game - to say the game flops because of that its an overstretch that discards many other things like interface issues, complicated systems, a combat engine that may put you randomly in bad start conditions... there's a lot to investigate on the reasons for its failure. Also a big drop on active users in the first year is something that most games cannot avoid: after the initial hype is passed and new options come, many games loose a lot of active users: it's just a feature fo the lifecicle. To see if a game has been successful or not, I would care more about the number of active users it retains, than to the difference with the number of active users it had just after release.