NASA landed on the moon with 1960’s technology, not because it was easy in the 60’s, but because every single aspect of the mission was planned, tested, rehearsed, and made as simple as possible where it couldn’t have a redundancy. The only time something went really wrong was when a faulty tank exploded on Apollo 13, but due to having an entirely separate craft in the form of the lander attached, the astronauts were able to ride out the failure all the way around the moon and back to earth. Oh yeah, even the orbit they picked would let the whole spacecraft fly around the moon and come back to earth without having to do any engine burns.
Look at planned missions today. Launch the Human Landing system. Have it sit in space for an unknown amount of time while anywhere from 6 to 12 refueling rockets are launched to refuel the lander. Relight lander engines in earth orbit, go to moon, relight engines again to orbit the moon. Launch the Orion spacecraft with crew on board, this also must burns its engines once at the moon to enter lunar orbit. Rendezvous and dock with the HLS, transfer crew and supplies over. Undock Orion, relight HLS engines for a 4th time to deorbit and land HLS. Use an elevator to get from HLS to the lunar surface for the next week or so. Board the HLS, which needed at least 6 refueling tankers full of cryogenic fuel to get to the moon and has now been sitting on the 200 degree lunar surface for a week, and light the engines a 5th time to take off and enter lunar orbit. Rendezvous with Orion, and return home. NASA has demonstrated that Orion can do the mission. But HLS has not even shown the technical capability of doing this. Its engines have never been relit in space, it has never sat in space for a week to see what happens to the engines. The entire interior isn’t even built yet and NASA is just using a 9 meter steel circle to train astronauts on the airlock section because no one knows what it will look like.
This mission couldn’t be more complicated if you tried. Apollo needed a total of 1 engine relight on the transfer stage, and 2 engine relights on the command module: one to enter lunar orbit, and one to leave and return to earth. The lander used pressure fed engines that only needed to work once each. One engine got them from orbit to the surface, one got them from the surface to orbit. If the Ascent engine didn’t work, NASA had plans for everything from literally jump starting it with the descent module’s batteries like it’s a dead car, to having an astronaut use bolt cutters to cut the safety pins on the engine so the valves can be manually opened.
If your car doesn’t start in the morning, you might call off work and get it towed to a mechanic. What do you do when you’re trying to leave the moon, and your rocket engines won’t light because they’ve been sitting in space for almost 2 weeks? The nearest rocket engineer is 240,000 miles away back on earth, and so are all the spare parts. And what do you do if only some of those engines light, and the others either don’t or explode while you’re on a suborbital trajectory. Complexity kills on harsh environments. Space is one of the harshest environment we’ve ever been in, so things need to be as simple as possible and known to work.