It is, but not quite as badly as the map suggests. The map only shows painted lanes and protected tracks, but doesn't really show the quietways and similar backstreets routes which are created by simple bollards and no-motor-vehicle entrances - or actually a few major no-motor-vehicle routes like the new restrictions at Bank. Those appear as dots on the maps, as only the restricted little bit shows up - I'm actually surprised that a certain Dutch city is quite as complete as it looks, because they also seem keen on connecting dead-end-except-cycles roads with short stretches of cycle track.
Nevertheless, I think a large part of the challenge of cycling around London on a bike is finding good ways between to move between the easy routes and it's part of why some stretches of overcrowded routes like Regents Canal remain overcrowded because the nice alternatives aren't obvious.
