It's not obligatory for anyone to have a development edit, but one can help wherever you are in your writing career. It's a question of choice. One thing is for sure, an outline isn't prose and writing craft, all it is, is structure.
I've outlined a trilogy and haven't paid for any how to books. I didn't use software, but it was quite a lengthy outline.
I wrote a blurb for each as I envisioned the story. I also determined the theme for each book.
I expanded that to 3x 2 page synopsis to include the endings.
Then I made a character list and backgrounds, together with what arcs they would have, if any. Over the three books there are around 20 characters, even a dog and differing POVs in some chapters.
I created a map of the world I envisioned after researching political, racial statistics and outcomes of sea level changes in the country.
Then I carried out research on the subjects involved in the story, including the US constitution, and copied and pasted the links.
I have an ebook template I always use with sixty chapters laid out to give me a 90,000 word book at an average of 1,500 words per chapter, and within each of the book templates, I marked out in red where I wanted the inciting incident by and the mid-point, then the end of the first act, then the end of the 2nd act and the beginning of the 3rd act.
The first two books, I did short paras of the story progression in each chapter, but I was lazy with the third book, which I've struggled finishing, having 17 chapters to go.
The first two have been to a development editor, and so will the third when completed this month. All the outline has done is to help me write all three books on just over 4 months and to get my facts straight within a three act structure.
I don't care how you outline or how long you've been writing,(in my case 10 years) the best laid plans need a professional eye to make sure you have not erred by being too close to the story and characters. At the very least you need beta readers, but they won't be as thorough. As indie authors we don't have a literary agent who would do it for you to make the story the best it can be before trying to sell it to a publisher, so if you like, the development editor stands in their shoes
The two books that I had to a developement editor, following recommendations, both of them, I moved chapters around and deleted one completely. Others I took scenes out and merged with others. There were quite few instances of changes that were suggested to improve pace and for consistency of character actions and dialogue that was out of their character. Parts of scenes I could make active where I could improve by using show instead of tell, etc etc.
Long and short is, the books are 100% improved by having a development editor go through them. Below is the link for my development editor who provided an excellent in depth development edit
https://www.kboards.com/index.php/topic,326629.0.html.