Direct election of senators had been proposed as early as the 1820s, and picked up support over the years. By the time the amendment was passed, 29 states had enacted some form of direct election on their own. Unless an amendment that not only repealed the 17th, but forbade the states from allowing direct election was passed, there's little reason to think much would change. People like the idea of electing their senators, and you're going to have to work hard to convince them to give up that right.
Because the Senate is a collegial body, where compromise and deal making is the only way forward, Senators can operate on the national level in a way which pleases a good number of people within their state, but which may not best help the state itself.
Because of the 17th, our Reps and our Senators are very similar. But in fact they ought to be serving different masters. I think the growth of the Federal Government was greatly asssisted by the removal of Senators are true advocates of their state legislature.
While it is true that many people for a long time wanted popular election of senators, this article points out that the Founding Fathers understood that many people might WANT that -- but that they should not HAVE that. It was supposed to be blocked, but the change got through anyway.