What’s hard is managing complexity and dealing other people on large projects.
This really isn’t surprising when you think about it by comparing writing of code to writing of spoken languages. Just because you’re excellent at grammar and spelling, allowing you to write great emails and possibly even essays, does not mean you have the expertise to write a good, cohesive, long novel.
Similarly, making a short video by yourself or with a few friends is achievable for most. But making a full length feature film requiring the collaboration of 100s or 1000s of individuals while keeping to budget is no trivial task.
Really valuable programmers understand that the actual coding is only a small part of being able to deliver a large successful project, where the real hard part is preventing the complexity of a code base from overwhelming your team while effectively communicating with others to ensure you build the correct thing which works cohesively.