Well, I have a sweet spot for Civ1 because it was one of the three games that came with my very first PC.
Funny enough, the best I can remember about the game is not related to the gameplay, but it's when I was figuring out the copy protection (you had to pick which techs lead to which).
It felt more rewarding to pick the answer from memory rather than look it up.
Now, as to the actual discussion, I think one of the factors that might contribute to this feeling of sameness is the importance of land grab in Civ and AC.
Theoretically, these games had a bunch of corruption mechanics in place that should discourage just sprawling all over the map (I remember AC being a bit better in this regard comared to CIV2-3),
but in the end, expansion was always the superior choice.
This lead to your empire being a blanket of noname 1-2 pop cities, with only a bunch standing out... and even those would be same-ish
from game to game, as you discovered the most optimal path through the tech tree and wonders.
Now a game that hasn't come up, but probably should, is Sid Meier's Colonization. I have a bunch of issues with it, but I think mechanically it at least attempted
to fix the above problem, because you had to setup entire production chains based on available resources, the entire logistics chains, as well as a way to dump
the product. This way your cities had to specialize and you couldn't just blindly carpet the entire land and had to account for your neighbors, European powers, etc.
All this was a delicate balancing act where you didn't want to rely too much on Europe, and you also had to to manage your relations with the natives and other europeans.
There was also the ultimate goal of achieving independence you had to keep in mind, which meant keeping the liberty sentiment up (limiting the influx of immigrants),
as well as to prep for the inevitable showdown with the king.
There was one other game I remember which tried something similar, Pandora: First Contact. It's an Alpha Centauri wannabe (it has it's charm), but with an external endgame threat as a twist.
Haven't played this one in ages, and I think I might have missed a DLC for it.