Look give it another 100 years and we'll be back on canals whether we like it or not. Might as well invest in them now, instead of spending enough money to buy a country that already has high speed train lines on a single high speed train line.
I'm not suggesting we could use canals to shift the quantities of freight that currently travels via trains and roads. I am suggesting that an upgraded, refurbished canal network could be a cost and energy efficient, low impact part of a decentralised, deconsumerised economy. There are some things for which canals are well suited, eg building materials which are rarely ordered or required on a 'just in time' basis. Timber, which often comes from remote places where rail freight facilities aren't available. If we can't use canals to get door to door, 24 hour deliveries of electronic tat made in a Chinese sweatshop and packed and delivered by amazon workers half dead from overwork, well so much the better.