I also think that RIIA is not a fully useful replacement for exception handling and having a finally. BTW, I also think RIIA is a bad name all around. I call these types of classes 'janitors' and use them a LOT. 95% of the time they are neither initializing nor acquiring resources, they are applying some change on a scoped basis, or taking something already set up and making sure it's destroyed. This being the official pattern name obsessed internet I get abused for even suggesting my name might be better.
I just don't think it's reasonable to require that that every complicated setup of some ad hoc list of things has to have a class written to contain it in order to avoid complications when cleaning it all back up in the face of needing to catch multiple exception types if something goes wrong in the process. This would lead to lots of ad hoc classes that just wouldn't be necessary otherwise.
Yes it's fine for classes that are designed to manage a particular resource, or generic ones that are designed to handle a set of similar resources. But, even if all of the things involved have such wrappers, the coordination of cleanup may not just be a simple in reverse order invocation of destructors.
I think it makes perfect sense for C++ to have a finally. I mean, jeez, so many bits and bobs have been glued onto it over the last decades that it seems odd folks would suddenly become conservative over something like finally which could be quite useful and probably nothing near as complicated as some other things that have been added (though that's just a guess on my part.)