the biggest thing they broke, which still isn't fixed to this day, is handling boxes with multiple internal links between the CPU and the switch
in some cases it's not handled at all (mvebu) so you lose some routing performance
in other cases it's been hacked in (mt7621), but you get optimal routing performance at the cost of a usable switch port
the wan port on my access points *is* physically part of the switch, but if I put it in the bridge, packets get forwarded in software