Thankfully, I don't have to make a decision on buying Civ VII today, and can wait for more news.
At this point, it doesn't increase the odds that I'll buy it. But I don't see it as the Worst Idea Ever, either, though certainly one of the most unconventional ones in series history.
Take away the actual civ identity switching, and just have it be "choose a set of ideas that will define your Civ in the next age", with the same sets of ideas available, and I suspect it would be a lot more popular. Which is kind of what Millennia has done - four times per game you choose one of approximately nine sets of ideas that define your civ for the next two ages. You're still called "Japan" if you started out as Japan, and your city names don't change, but you could pick Viking-inspired raiding bonuses, or Greece/Macedon-inspired military bonsuses, or Egypt-inspired building bonuses or various other ideas, all of which essentially amount to civ switching but while not "becoming" the Vikings/Macedonians/Egyptians/etc. You're just choosing to follow a similar route for that time period.
That's something that Civ VII could offer as an option as well - maybe you choose the ideas and bonuses of Songhai or Shawnee for the Exploration Age, but you have the option to keep your identity as Egypt. I could see that defusing a lot of the criticism around immersion while being mechanically the same.
I also find it interesting how before Humankind's release, there was a lot of excitement about the idea of civ switching, and after their implementation of it was generally poorly received, there's now so much angst about Civ trying the same idea. It makes sense in a way, if you saw the Hindenburg crash in New Jersey, you'd be more hesitant to fly on an airship in the future, but if Civ VII had been announced prior to Humankind's release, I suspect the reception would be at least somewhat different.