It's easier (or as easy) to change gerrymandering as it is to change the senate back to it's intended purpose. If you want to argue that an amendment to make gerrymandering unconstitutional should be a prerequisite to returning to state legislatures selecting senators, I'm fine with that - because it's also a much more likely amendment to pass. A big chunk of Americans dislike gerrymandering. Only a tiny fraction of Americans know or care about the different chambers of Congress being intended to serve very different purposes.