Sending humans to the Moon is a massive technical undertaking, even with modern technology. The list of challenges includes life-support systems, water, food, sanitation, radiation, medical needs, communications… and the list goes on. All of the equipment and consumables needed to do those things need to be launched from Earth and transported to the Moon. Weight is at an absolute premium when transporting things to the lunar surface, so there’s a strong drive to reduce the mass of all of those things. But if you reduce it too far you run the risk of catastrophic equipment failures or running out of critical supplies. Balancing all those needs requires a lot of effort and will also need a lot of new technologies.