It is not difficult to find a solution to routing problems, the difficult part is to get probably near optimal solution (<1% optimality gap).
The issue is that there are exponentially many of them and you cannot easily rule out that there is no better solution than the one you have on hand.
That is why we solve these problems for as long as possible with as many resources as possible.
It is not difficult to find a solution to routing problems, the difficult part is to get probably near optimal solution (<1% optimality gap).