Darvond: Is this a ramble, or is there a point you're trying to make?
macAilpin: I dithered. Just thinking about how the series died out and how it happened.
I like your point actually. C3 is really an optimization game, a mathematical puzzle to create a city in which "walkers" (like prefectures, school children) walk by each house, markets have access to all resources and all buildings have access to labour (e.g. requires you to build a small settlement near your farms), and create areas with sufficient desirability.
In the more recent installments, like Pharaoh and Emperor, a lot of these mathematical challanges have died out by e.g. introducting road blocks and the "walls" in emperor that block negative desirability of nearby industry. I also play Anno 1800, and there are a lot of similar "ease of life" fixes in there as well, like a global labour pool (no need to create small settlements on each island) and fixed building area of influence (instead of walkers). Although this eases gameplay and lets you build nicer cities, it also makes the games easier, to the point that you don't really care about city layout anymore like the way one did with C3.
Maybe good to know: For C3 there is an open source reimplementation (Julius) and fork (August), accessible via
https://github.com/bvschaik/julius. With the Fork, one can enable all kinds of improvements (like road blocks and global labour pool) to make the game more on par with recent installments, which you may not like then ;)