Exactly right. And the voters of Colorado must have realized this last month when they rejected a similar dilution of their own influence.
If every state adopted district elections, it would increase their power. You're going to have to have every state legislature adopt it to make it effective. The only reason the WTA method prevails is cause we're used to doing it that way and politicians from the majority party in the states want to keep minority party voters disenfranchised. That's why we should try this simple reform before we go to the drastic step of amending the Constitution to change something we've had for two centuries.