True story, but they do fail. I've done flights on the E-175 with no AP and no A/T.
It's a lot of work. It gets easier the more you're used to disconnecting and flying, though.
Usually, but again, not always. I've had departures, properly built and loaded from the DB, that suddenly decided they wanted to turn the wrong direction into a literal mountain range in IMC conditions after rotation. When they first released the IRNMN into LAX, the airplane decided it—while in FLCH, climbing to altitude—that it suddenly would rather go into a straight vertical VPATH descent to -2000'.
I've seen primus epic decide that an RNAV departure off close parallel runways involved flying a lowecase letter 'e' as depicted on the FMS, or that it was a good idea, passing BRIXX on the BDEGA with lower set, to try to fly a vertical descending VPATH.
I've seen stuff like that while jumpseating on other transport-category aircraft, as well, but I'm not trained on those and can't verify it wasn't GIGO. In the case of the 175, I've also seen plenty of GIGO, as well as "techniques" pushed that don't actually work in the airplane / actual operational environment.
I generally feel that at the 121 level, the other important skills are continuing to mentally fly the airplane, creating and maintaining a mental model of the aircraft state and flight path, and making sure that the model is shared between the pilots. Yea it sounds cheesy, but realistically CRM is fundamental to safe operation when n>1.
But WTF do I know?
Signed,
-Basically a private pilot at this point