Mutual submission fails when applied consistently to all three household code groups

If verse 21 means everyone equally submits to everyone, then it must apply to all three pairs: husbands-wives, parents-children, masters-slaves. This would mean children submit to parents AND parents submit to children equally, and masters submit to slaves. Nobody in the first century thought this. Paul says 'submitting to one another' then gives three examples of UNEQUAL submission. The mutual submission interpretation would also undermine 1 Timothy's requirement that elders manage their children.