That's fair, and personally I love the idea too, but as someone who grew up in a city with a major commercially-significant canal, it's a bit overrated in reality and you are probably underestimating the traffic chaos it causes. Bridges can cause huge delays, are vulnerable to extremely dangerous allisions, and strictly limit the size of ship that can get through the canal. Even with tunnels, which likewise limit the size of truck that can go through, the constant maintenance (and cost, and lack of expandability over time) is a real bummer. If you're willing to limit it to relatively small ships like they do in Europe it's potentially manageable without too much fuss, but if you want big bulkers and container ships traveling deep inland you're going to find your road network ends up chopped up into loosely connected islands with big delays and traffic bottlenecks real quick. It's a pretty big compromise.

Trains do a much better job of interoperating and coexisting with existing road networks without majorly disrupting them. (and for what it's worth, canals mess up train networks just as bad if not worse than they mess up road networks)