I've felt that organically grown cities, of which most major European cities are good examples, are very sub-optimal for because of the haphazard and random way the cities are laid out. It many such cities, the old, medieval core became so bogged down that cars aren't even allowed and it's basically a pedestrian heaven.
Navigation is hard in these cities, traffic is usually a mess without modern development to route around the "organicness" of the city centers, as a result certain types of goods and services...namely anything to do with lots of manufacturing or bulk goods, ends up moving away from the city core. And while it means that the cores tends to become very pedestrian friendly, they really just sort of end up as extended outdoor shopping malls with some housing for the shop workers above.
It's interesting in some of the older Asian cities which have very old histories, say Seoul, the the haphazard, medieval-style organic planning has given way to a large effort to put the major thoroughfares on a grid and as old areas are redeveloped, to do so with a heavily planned development policy in mind. The city was simply not able to handle the growth and population demands the organic system created.
There's a reason Paris' business center is not in Paris' geographic center, and central London has restricted driving zones, and most of Barcelona's population enjoys the 19th century planned developed residential areas, while the older parts are being turned into tourist hotels, malls, restaurants and more shopping areas.
