> The problem of over-engineering isn't just related to the big PHP frameworks - the same problem exists in Python and Ruby.

OTOH, the "complexity" may also be "configurability" or "pluggability" with missing shortcuts. And quite often the "simple" version ends up being insufficient when one needs to tweak something: http://lucumr.pocoo.org/2013/2/13/moar-classes/

> That's a fairly simple concept

When going for pithy statements and omitting most of the actual issues, even encryption, clustering or networking "[are] fairly simple concepts". Which effectively they're not.