Even though I've dealt with this, I'm genuinely appreciative of requirements: out of many stipulations, packages that monkeypatch are prohibited (I have a few ones that add diagnostics to advance analyses), online API access needs robust error handling... and there is a conformance/diagnostic suite.

https://cran.r-project.org/web/packages/policies.html

Yep, as someone who both uses lots of R packages and writes lots of R packages (which, in turn, import other R packages), I've grown to appreciate the strictness of CRAN: if a package is on the CRAN, I'm just about guaranteed to not have installation issues or have it screw up my environment. To me, that's the one major job of a package repository, and CRAN does it well, even if it does cause package authors pain at times :)