Both defer and RAII have proven to be useful, but RAII has also proven to be quite harmful in cases, in the limit introducing a lot of hidden control flow.

I think that defer is actually limited in ways that are good - I don't see it introducing surprising control flow in the same way.

But of course what you call "surprising" and "hidden" is also RAII's strength.

It allows library authors to take responsibility for cleaning up resources in exactly one place rather than forcing library users to insert a defer call in every single place the library is used.