Hello, can one part of the performance problem be, that default style is rendering e.g. buildings in z=12? Ok, I can see extrem large buildings like the terminal from airport Berlin-Tempelhof in this zoom-level but the most buildings have subpixel dimensions. So perhaps somebody is interested in style optimisation. Especially with a view to what Wikipedia really needs, so IMO we could live without "amenity=recycling"...
Greetings Kolossos