Always good to challenge the narrative - but I don't pay for RDS Postgres because of the WAL, replication, all the beauty of pg etc. I pay RDS because it's largely set and forget. I am gladly paying AWS to think about it for me. I think at a certain scale, this is a really good tradeoff. At the very beginning it could be overkill, and at the top end obviously its unsuitable - but for most of us those tradeoffs are why it's successful.

You can use stuff like Litestream to continuously back up your SQLite DB to a cheap storage bucket. It's practically set and forget too.