One of the problems with the old way of selecting senators was that it turned state legislator elections into votes for senate electors. Remember the Lincoln-Douglas debates? Those weren't about swaying state legislators. They were about swaying voters who would elect legislators who would vote for them, and that issue dominated the election far beyond any state matter the legislators faced.
Then there was the problem of corruption, and several scandals showed it wasn't hard to bribe your way into a senate seat when you only needed to sway a few state legislators. And when that didn't happen, senators were usually simply cronies of whatever political machine was running that state.
For those and other reasons, most states had gone to some form of direct election of senators by the time the 17th was proposed, which is why it sailed through ratification very quickly.
That is an attribute, not a problem. Our state legislators should be aware of national issues. When held once again to higher standards, we'll get better legislators.
The way to deal with corruption then as now and in any age is through legislation to punish corruption. It is no reason to destroy the liberty saving feature of federalism.
The 16th and 17th amendments sailed through because beginning in the late 19th century, the evil of progressivism had infected our body politic. Progs love democracy, because demagogues are powerless without it. It is as easy a sell now as it was then. Progs are moving now at full speed to nationalize presidential elections.