1) There is much more to the interactive development experience than the REPL. As mentioned in the article, the debugger and inspector are key parts of this workflow.
3) It's not that software is released too far apart, it's that the release of software is out of the hands of developers, and packaged by a third party with dependencies that may not even be API compatible with the developer's software. Since there is no versioning dependency management for Quicklisp to leverage, all it can do is try to build your software in isolation, not check compatibility with dependencies, and certainly not runtime compatibility.
3) It's not that software is released too far apart, it's that the release of software is out of the hands of developers, and packaged by a third party with dependencies that may not even be API compatible with the developer's software. Since there is no versioning dependency management for Quicklisp to leverage, all it can do is try to build your software in isolation, not check compatibility with dependencies, and certainly not runtime compatibility.