yea,
well - sort of: these advanced approach ( & autoland) systems are really complex: some planes have 2 or even 3 autopilot systems - they check with each other for agreement, etc. the air data sensors and all kinds of other systems must agree - anyway: I say all that to say that we must fly the approaches - it can be done in the cockpit or the sim, if there are faults - you report them (radar altimeters disagree etc) and the system is checked.
a little history: Aviation had been thoroughly plagued by equipment failure in the past - many more pilots died due to bad design, manufacture, or assembly than to human error (or even combat).
so inherently, we don't trust computers, engines, fuel ourselves, or controllers. That is why we have 2 computers, 2-4 engines, many fuel bladders, co-pilots, and radar.
anywho - this issue of co-pilots goes deep into human factors: a wide and vast field - some folks who are into HCI may have studied some parts of this - and from this we have learned that having at least two in the cockpit is way better than one (three is even better). Just please understand that a co-pilot is NOT a backup pilot in case the pilot has heart failure. he/she is an integral part of a team that keeps the plane going where its intended to be.
j