I honestly think one can boil down a retirement plan (a really good one) into thirteen words:
"$5,500 annually into an IRA or 401(k) invested in cheap target retirement funds"
Okay, sure, you can argue that this plan (which will typically only get someone into the top tenth percentile) takes too long or comes up short.
But something that can pretty reasonably be described with a short phrase seems pretty DIY-able.