Low skilled people tend to overestimate their abilities and underestimate challenges.
Put simply, we suck at estimating difficulty of tasks when we have little relevant skill. This is compounded by ego. Some people with some skill level in subjects like game programming, graphic design and game design, vastly underestimate the challenges in making a successful commercial release. This is further evidenced by the number of prospective developers seeking to build open-world MMOs with small, volunteer teams. They do not have enough experience to realize what they are attempting is impossible with their available skills and resources.
More recent research has revealed that Dunning-Kruger effects are not as universal as initially thought. Only relatively small proportions of a group are prone to severe overestimation of abilities.