GTD is not for creative work. GTD is great to deal with type 2 procrastination [1] because not everybody can afford to have somebody doing their important errands. So it is just an efficient method of preventing my (your) life to become a mess. Listing every micro action in a fancy way (in my case I use Evernote [2]) would be wasted time (that is better spent deciding what is the next action or doing real work), a sheet of paper is more efficient for that.
I don't agree that it is not for creative work. I think most people just don't understand the process of creativity enough to be able to think about it on a meta level.
Your TODO list is meant to be an extension of your short-term memory, not long-term. It's not a log of activity. It's not a planning document for assigning deadlines and figuring out project length. It's low-friction reminders of whatever you need reminders for.
Haven't you ever been working on something and realized there were two different things that had to be done, but in different directions? If you write a TODO for one of them and start working on the other (without writing a TODO for it), then you won't have to break your flow just to remember the other item thereafter. It's okay for things you do to not be on the TODO list, and it's okay for TODO list items to only live for 15 minutes, so long as it is longer than it would live in your short-term memory.
A TODO list is not ever meant to be completed. Things go on it and come off it, it grows and shrinks over time, but it's meant to be a living document. If you're having problems with your tasks being too large and nebulous to appropriately use on a TODO list, then your first task is "break job down into more tasks."
Maybe I didn't explain well but In practice I do exactly what you say: I use GTD mostly to list delayed type 2 actions (ex: doctor appointments, bills to pay, etc), long term plans and project briefings. Small actions are listed roughly in a sheet of paper as an extension of my short term-memory and only if I have a lot of them in a given moment.
> Haven't you ever been working on something and realized there were two different things that had to be done, but in different directions?
Yes, but who ever needed a TODO to remember that other thing? It's all part of the whole that you're trying to build, you understand what it's going to look like and why you're doing it like this, and of course after this part that other part also still needs doing. You don't need to remember it, it's part of the bigger picture.
I write down reminders for things outside that, like people who wanted to ask a question, mails I need to answer, errands. Things that are hard to keep track of because they're not about the thing you want to be thinking of. The main thing you're trying to make doesn't need them.
The creative process progresses when ideas come out subconscious processes, like when you take a morning shower. Todo lists are very conscious things.
I don't know if I fully agree with the GP's idea that this is the canonical definition of a TODO list, but I don't think short-term memory alone is sufficient for the current project in all cases. For the creative process of design I tend to agree you usually don't need to keep notes, but for the creative process of code architecture I think external notes are often necessary, especially if there is any significant refactoring of existing code involved.
One problem is that creative tasks can't always be broken down into more tasks. The other problem is that the whole practice of religiously creating todo's is pure horror to some people.
Many of the more extreme 'artisty' types of people I know absolutely hate any form of task management beyond a simple list. Preferably on a post-it on the wall or on a scrap of paper. The way they feel about simple task/project management apps is probably how many 'less-extreme artisty' people feel about GTD. It just doesn't click for many people.
I don't generally like to think of my TODO list as a scheduling tool, but I do like giving larger tasks greater representation on the TODO list. So even if all I had to do was "fill this entire notebook with hand-drawn squiggles", written as a single task doesn't convey the full weight of the task. So I will explicitly repeat the task on the page several times, until the "weight" of it feels more appropriate.
It's not explicitly scheduling the tasks, but it is at least giving a better representation of its relationship to the other tasks going on in my life. I can't say "I'll make lunch after I'm done with <this big task>" if the task will take more than a day to complete. But I can if I chunk it out in this way.
[1] http://paulgraham.com/procrastination.html
[2] https://github.com/we-build-dreams/hamster-gtd (a simple implementation that you can use as a starting point)