The B741 was an extremely problematic aircraft yet is still one of the most successful aircraft in the sky. It shared the same new fears and awe.
The 747 had no safety issues, no in-flight fires, was not three years late on first delivery, managed to deliver over 100 to the airlines in the first 18 months, pretty much at the original dates specified when orders were placed, and of course was not grounded by the FAA, in days when their oversight ability was way greater than now ......
It did have significant issues with the JT9D powerplant (most commonly by going slightly oval and abrading the seals). There were a number of in-flight shutdowns but it was a quad, and in all truth the shutdown rate was little different to what the 707/DC8 generation had experienced beforehand. Most JT9D issues were actually caught before departure, so there was some unreliability. It also had multiplex issues with its electrics. Of course, those were the days when aircraft were designed properly, so there were only cabin comfort items etc, not any critical features, using the multiplex. Boeing's designers in the late 1960s wouldn't have been so silly .......