I agree with this. I think the whole "history in layers" pitch and the attempt to frame these new mechanics as "historical" is absurd, especially the way they set it up, e.g. having Greece switch to the Normans or Hawaii becoming America.
FXS just should have been straightforward about it, that they came up with Civ Switching, because making new Civs is far less complicated than having new 3D Leader models. Plus, for some obsure reason, the Devs seem to love the agendas (whereas I think most players don't), and these work much better with leaders than with civs.
The easy solution would have been, to give the players and the AI the option to keep the existing Civs, if they wanted, and let the players, who focus more on pure gameplay mechanics, mix Leaders and Civs as they please. That would have spared us lots of controversy about who should be the predessor of who and how these different "unlocks" should be set up for each specific civ.