Hey Andrew! It's great to see you here. I agree with everything you said, 100%. I'm honestly torn because I was the first one to recommend `if_not_exists` to engineers, but now I'm reconsidering because this can lead to very strange issues in production, especially for ActiveRecord applications. Maintaining an "invalid index reaper job" doesn't sound like a good long-term solution.
I've suggested some proposals to Rails here and would love to propose a PR based on the solution that makes the most sense, too.