I travel a 25 mile distance to work to find the same 4. If I travel an extra 15 miles north to a friends', same deal. It's not a matter of how much you move around.
Your comment about big buildings and factories is why you find the same 4 everywhere; because what determines finding different Pokemon involves actually going to largely populated blocks in a city. Rural players get the short end of the stick because the game focuses on locations with the highest cellular data to increase spawn rates. Big cities, or major areas such as Santa Monica pier or Central Park have incredibly huge spawn rates. All of this is due to how Ingress was developed & how XM concentration was usually founded by a couple theories involving where the highest data usage was, where the most Ingress players were playing, and even WiFi hot spots. In short, areas with a lot of activity.
So, if you want to find better Pokemon in the game, it's not a case of walking around your area. It's a case of finding out where XM concentrations (which influences Pokemon spawns) are highest in your city, and going there, which turn out to be large cities and parks.