If you fail to notice that, you fail to notice the fundamental difference between the two bodies, of course.
If you have a legislature vote for a Senator, the only difference between that and having everybody in the state vote for a Senator is the number of voters!
We have the same issue when it comes to appointing or electing judges. Pretty much the same sort of people end up being judges, but the number of folks voting is different.
Personally, I prefer as broad a base as possible in the electorate for every office.
BTW, I think you are raising this meaningless objection simply because I pointed to the problem ~ the poor quality and character of Senators ~ and the solution ~ one term and then execution.
Playing around with the number of voters isn't going to address quality and character and you know it.
Actually, the Legislatures were able to recall senators who disobeyed the state legislatures. If the same system were still in place, Republican Sen. Lindsay Graham would have been recalled last week for his little filibuster fiasco.
If senators don't tow the line of the legislature, they are recalled.
The difference is that the state legislatures were more responsive to the voters of their respective states. If a U.S. Senator did not represent his state, the state legislature could and did remove him. An example: Jim Lane of Kansas was removed as Senator during the Cvil War and wound up committing suicide rather than face prosecution.