Ah, right, I get that. Is it a question of mindset then: you're losing your Civ rather than evolving it?
There used to be very long arguments on this forum about whether the Roman Empire, Byzantine Empire, and HRE were the same civilization or different ones. This mechanic makes the question obsolete: you start as the Classical Romans, and then you choose to become either the HRE Romans or the Byzantine Romans. Granted this wont work for every era change and every civilization (not all have a clear antecedent or successor), but there does seem to be real effort to provide a "historical continuity" option at every step.
Evolving your civ make sense, but it also make sense to have the option to overcome the challenges that historically X or Y civilization could not. A lot of people would be more receptive and whiling to buy the game if we are allowed to keep the identiy of your civilization. Some would say "the point is to change", yes but you can change without be at a foreing invasion and cultural replacement level, there are also civilizations that changed just at religious, ideological(goverment) of even just at administrative(dynastic) level.
From a gameplay perspective
religion and
government "
revolutions" type could be as significative as
cultural revolutions. Even historicaly civ like Japan would likely have multiple versions (no way Firaxis would waste Samurai and Zero fighters) that certainly is not at the level of Aztec to Mexico.
Now, of course people could want some goverment and religion customization, so this could be still allowed. We could have cultural, religious and political (goverment) customization, just that when you pick a revolution centered in one of those aspects you gain more "extreme" uniques related to that focus, while the others two aspects are free to lesser customization. For example you can as England do a Communist revolution and get a lot of uniques related to it, or instead revolution from England to America and just pick a lesser Social ideology (Liberal and National are also options).
It is posible to build a set of religion and government focused revolutions that provide common uniques, for example what if as Roman I pick the "Holy" revolution and get uniques like
Monastery,
Inquisitor and the
Holy Warrior that for the visuals of european cultures looks like a crusader. These way we could roleplay as an actual "
Holy Roman Empire" doing some crusading around.
Well even the "civs used to be interesting in just a couple of eras" argument is quite ironic when now we are going to have more uniques than ever before, but look at the Maya we are going to get, a lot of uniques are very redundant about jungle to gain science+culture. Why instead of put those many repetitive unique elements in the ancient era dont distribute them as more significatives ones all along the ages? And yes the Maya are more than classical mayas, the post-Classic Yucatec and Kiche, the last peten kingdom lasted until late 17th century , then the 19th century maya Cruzoob state and even now the Zapatistas in Chiapas.