I agree with that.
I am saying that they go all over the states that are contested.
They would campaign in more states, but wouldn't they concentrate their effort on the large cities?
Even with your argument, they are still only campaigning in contested states (meaning about 20% of the country). And of course in those states they are going where they can reach the most people: cities. It would be foolish not to, really.
Without the electoral college, they will probably still mostly concentrate on cities -- you go where the people are -- but at least they would be doing it all over the US instead of just the few contested states.