Morgans writes:

As I understand it, this is one type of issue that could be greatly improved
when true "free fly" routing is in place. Take off in any direction that
will meet the needs, and not worry about the airways.

It depends on how much of the congestion is en-route, and how much is in
approach and departure. Free flight would help in the former case, but it
wouldn't make much different in the latter case.

Additionally, although truly random free flight would eliminate en-route
congestion, it would also raise costs, since most random, free-flight routes
are going to be longer than the optimal route. There would be a tendency for
everyone to try to fly the shortest route, and then the congestion would
return.