Wouldn't it make more sense to design it like Haskell? or something even more strict? A little bit of extra work seems like a small price to pay to prevent millions being stolen from your wallet because of a silly mistake like this...

In Haskell everything is public by default unless you specify exports for the module.

But it also has a statically checked type system.

I think if done in Haskell how good or bad it is depends on the chosen abstraction for effects not Haskell itself.

Haskell is a good basis but the developers need to make the API fool proof. E.g. expose limited effects rather than a big fat "IO" type.