I don’t think repeal of the 17th Amendment is an imminent threat, and my first instinct is to embrace any old form of hating on the existing structure of the US Senate, but on reflection we should probably stick with direct election of Senators.
A cautionary tale about indirect representation is offered by Germany’s Bundesrat, a sort of somewhat-disempowered Senate that is appointed by Germany’s version of state legislatures. The problem with this is that people wind up voting in elections for the Saxony or North Rhine/Westphalia parliament based on their views about federal politics. And there’s really no “right” way to answer this question. Ignore federal issues in your state parliament voting, and you’ll be accidentally impacting the federal scene. But if you vote on federal sentiments, then you’ll be ignoring important state-level issues that are worthy of consideration. Already in the American system people’s votes for state legislature seem unduly influenced by their ideas about federal politics. Further entwining the two is only going to lead to poor governance.