The idea that a SAPR (Synthesis, Auto Place & Route) flow is fundamentally inferior to a full-custom layout is tenuous at best. It's really just a new parroting of the good-old days cliché.
Modern gate-mapping, placement, and routing algorithms are quite sophisticated these days (and improving all the time), and computers are incredibly fast, relative to a human mind. Could a really good layout engineer do a full-custom 64b carry-lookahead adder that is smaller, faster, less power than an automated flow? Maybe. But how long is it going to take him to do the whole FPU? Or how about a complex block with upwards of 1M logic gates? Hand-layout for digital logic has rapidly diminishing returns, in my opinion. Better to have your layout guys do some awesome stdcells, and let the tools and PD wizards do the rest. In many cases, it'll be just as fast (if not faster) than the full-custom option. Note well that automated flows don't explicitly demand random/non-structured P&R algorithms.