This is actually a huge strength for the R community, who by and large are not programmers and just want stuff to work. The fact that the latest version of all CRAN packages actually work together makes life much easier. And for experts there are tools like packrat and checkpoint that give you more control.

I'm sorry, but this mindset is very harmful. If I need an old version of a package and I didn't save it off somewhere first, it simply cannot be found.

Huh? There's an archive link on the CRAN page for every package; e.g. ggplot2 back to 2007: https://cran.r-project.org/src/contrib/Archive/ggplot2/

packrat and especially checkpoint to the rescue!

Checkpoint only allows specifying that all packages as they existed on a particular data in CRAN be downloaded and utilized within a project. This is limiting in that an R developer may want to utilize very specific versions of packages that span multiple epochs.

I would really like to see R develop functionality akin to Maven or SBT, such that an R developer can explicitly specify the exact versions of all dependencies, which will then be installed at the first run.

That's the goal of packrat. (But it's still a work in progress)