It´s just the same with me. After the year 2000 there are only hyper-modern buildings and there´s no possibility to stay in the here and now. But there´s at least this mod. The first era buildings are though replaced by more modern ones, but at least the 2nd era building stay forever and that produces a more realistic cityscape...
http://steamcommunity.com/shar…filedetails/?id=802421382
And if you activate this mod, there will be all town buildings available, so all eras are mixed. So the first era buildings stay in later times, but in my opinion, this doesn´t look great direcly next to very modern architecture.
http://steamcommunity.com/shar…filedetails/?id=799823150
These are at least some approaches, you could use, but I would support it, when somebody will make a mod like you wish.