I would say that it is mainly a question of training and experience. Then there is also the scope of the project that plays a role. Launching into an idea that is too complex risks leading to an unfinished game, therefore potentially not funny and/or not polished.

Besides experience, I would also recommend learning your tools well. Game engines, IDEs and drawing programs provide many shortcuts and tools that would help you create things faster. A good habit to develop is to be mindful of things that take you a long time to do, and search google (or chatGPT) if there's a shortcut for them.

For example, most IDEs would let you jump to a file by typing it's name instead of having to search for it in the files tree and click on it with a mouse. This is a HUGE time saver.