How do you "insert yourself in the loop" on a FBW plane when the computers conk out? There is manual reversion on an Airbus but it is very minimal - if you ever

How do you "insert yourself in the loop" on a FBW plane when the computers conk out? There is manual reversion on an Airbus but it is very minimal - if you ever end up in a situation where that is needed you are having a very very bad day. On the other hand, 737 is actually fly-by-wire - literally, because actual steel wires are still connected between the cockpit controls and the control surfaces. So if the electronics dies and the hydraulics isn't working neither for whatever reason, the plane can still be controlled. These "magic boxes" are there to augment the control characteristics, such as the "feel" of the control column (which is normally lost due to the hydraulics driving the control surfaces). Or, in the case of MCAS, to help with an aerodynamic issue. Both are hardly unprecedented - the last large transport plane that didn't rely on any computers/electronics for controls was maybe the 707. The problem is the poor design of the MCAS software/system, not that it exists as such.