While a twin engine has redundancies that may add to safety, it also adds complications when system begin to fail. It is statistically proven that while single engine aircraft failure may result in more unintentional landings/crashes, the survival rate of that is much higher than when a twin loses an engine and crashes. Flying a twin on one engine is a task due to asymmetric thrust and drag that can quickly lead to stall/spin if airspeed is not maintained.
Additionally, most of these accident both twin and single occur in piston driven aircraft. Piston engines have much higher failure rates than turbine aircraft. The Pilatus, the Cessna Caravan, and many other turbine aircraft are highly reliable, and when you do lose an engine, are pretty easy to dead stick to landing.
I disagree with your comment that complications are added when systems begin to fail. A twin engine aircraft supplies two sources of electrical power, two sources for hydraulics, two sources for pressurization, two sources of bleed air for deicing and secondary systems (such as door seals, hydraulic reservoirs, etc.).
I disagree with your comment that flying on one engine is a task due to asymmetric thrust. When a multiengine aircraft is certified by the FAA, the maximum allowable rudder pressure during single engine operations is 150 pounds. That would only occur during high power, low airspeed situations, like the initial phase of take off. Losing an engine in cruise, descent or landing is a non-event. In fact, it’s not even an “emergency” in the checklists in the later Boeing products.