but no government has simply given up land and cities too another because they had great art.
Which is what Civ IV's system seem to represent.
Well, as I see it, Civ 4's system represents extending and consolidating cultural, ethnic, etc. influence over an area using stufs like great art as a representation. Sure, the Mona Lisa probably won't get that nearby city over in Germany, but if you use your imagination, it does all right at representing making an effort for extending your indirect influence over an area.
Depending on how you want to see things, stuff like what Civ 4 did has happened historically. Texas, for example, got an absolute flood of immigrants from the U.S. that identified more closely with their homeland than Mexico. Eventually, Texas ended up rebelling, and after a stint as an independent republic, it walked into the U.S.'s hands. I imagine that's essentially what goes on in Civ 4. The people identify more closely with your nation, and, should the other nation's military presence be sufficiently weak, they rebel and join up with you.
Now, diplomatic consequences of accepting land and such that the other government considers its own aren't quite dealt with to the fullest extent, but, y'know...
I would like it if you could ocassionally steal tiles that border your physical borders with superior culture but nothing in like civ 4
Wouldn't, by your own argument, it be silly for great art to steal even a few tiles?
It doesn't seem like you can just say, "Well, the Mona Lisa can take some kilometers for you, but not a whole city or nothing." Is great art what's taking that land or isn't it?
So, y'know, food for thought on what culture in Civ 4 actually represented.
Or like in Civ IV when you conquer an enemy your new city would be completely strangled by their culture.
The way I consider culture in Civ 4, that's basically how it'd go. You've got your little conquered enclave sitting in the midst of a whole bunch of people who don't identify with your culture, your government, and so on. I mean, yeah, it's unfortunate that you can't hold up a gun and make the nearby folks work those tiles, instead of just sitting there trapped in your starving island-city... but as it goes, it does make some sense.
So, yeah, I'm a little disappointed that you can't culture-flip as in previous civilizations, but I suppose I can get by.