Frankly, I don't think so. I feel like you're the one with the tainted-glasses looking back with some soft nostalgia. I don't know the switch from III to IV, but I vaguely remember the switch from IV to V and definitely remember from V to VI. Edit: for a more recent example, I remember the second-hand backlash that Eleanor and leaders leading different civs brought to the game, with the most inane takes on it and some of the most over-the-top hyperboles on what it would entails for the future of the franchise.
And, frankly again, the whining and tantrums I see here for this "feature that'll kill the franchise" is broadly the same amount of whining and tantrums we had for any element that changed through any other change. Plus ça change, as French people say.
Now, I'm not saying that, since any tantrum threw in the past ended up becoming a beloved feature, that people throwing tantrums over the civ-switch is proof that it'll become a beloved feature. But from my point of view of having played Civilization for roughly 20 years, it definitely has the same feel, as far as I can remember.