I suppose it’s inevitable that people are making comparisons between the latest Lunar orbiting mission ARTEMIS II and the similar Apollo 8 mission of 50 years ago.
The original Apollo mission made 10 orbits of the Moon whereas the Artemis II mission just looped around then returned to Earth. So the question is why did the Apollo mission take just over 6 days and the Artemis mission took much longer: 10 days.
I originally did an article on orbit types and times over 2 years ago in which I explained the Hohmann transfer orbit and how it needed the minimum Delta V to arrange. Or in plain English, the simplest way to get to the Moon is with a small boost from a circular Earth orbit so that the resultant ellipse encompasses the Lunar orbit. It’s also like playing swingball, the harder you hit the ball the bigger ellipse it makes.
The problem with just using a small engine burn or burns, is that it takes more time to get there, using a more powerful burn gets us there faster. It all depends on how much life support the spacecraft has, if there is enough for a longer duration flight you can take a slower path. The Apollo missions had life support for 3 people for 10 days so needed a faster transfer, the Artemis capsule is designed for a longer duration flight, 4 people for 21 days, hence the change in flightpath.
All this is part of the planning for longer duration flights that the later Artemis flights will make as the building of a lunar colony progresses. In many ways this first flight was the easy one, purely to test the systems and make sure the capsule works. There is still the lander to check out, by actually landing it on the Moon, and a host of other new equipment that’s never been tried before. You need to be brave as well as smart to be an astronaut, testing new systems in space isn’t for the faint hearted.
So what will the next mission Artemis III be doing? This one will be flying in Earth orbit and testing the lunar landers, built by either blue origin (Jeff Bezos company) or by space X, no decision has been made yet. Artemis IV is planned to actually land on the moon in early 2028, if everything works as planned. I doubt very much if everything will work, the history of spaceflight is full of problems and I don’t think this time will be any different.