Type inference does not mean untyped. Arguably, getting a type error when you didn't write a single type hint makes things even more confusing if you are not an experienced programmer.
> more effort needed to create error messages that are helpful to the user.
Well, sure, but that's a tradeoff for the developers of the language to consider. As a user, there are already plenty of statically typed languages to choose from with many person-hours put into just that.