Dawn of kitchen sink libraries in Ruby
codemancers.com
codemancers.com
I understand the concerns the author is raising and having a single responsibility for a library is definitely ideal. But as far as I have experienced, file uploads are never as trivial as author is pointing them out to be.
Most of the times you need some kind of post processing for the files, sometimes you need multiple file uploads, sometimes you want to do it asynchronously. It just never ends up trivial.
I support the idea of a framework essentially being a light-weight layer on top of libraries, but if the framework just uses a single monolithic library then little (but something!) is gained. If it uses one or more libraries that are all properly composed of smaller modules, etc, etc, then a lot of flexibility is gained.
I'm not very familiar with Rails - especially its internals - so it's hard to comment on this particular case. However, making job queueing modular seems to have found the approval of most people in the commit comment thread you linked.
But I agree that the distinction is never clear cut, and everything needs a discussion on a case-by-case basis...
gems are becoming cpan...