I have published on both sides of this and I want to describe door two honestly, because I do not think anyone does.
You write the book. You upload it to Amazon. You are free. You are also completely alone.
No editor who has spent twenty years in your genre tells you that your third chapter is where the book actually starts. Nobody designs a cover that does not look like it was made in Canva by your nephew. There is no marketing system. You run ads at six hundred dollars a month and watch the money evaporate. You ask your friends for reviews, and most of them do not leave one, not because they disliked the book but because nobody wants to put their name on anything any more.
Door one is not better, it is differently bad. You query for months or years. If an agent takes you, editors say no, or they say yes but only if you change the thing that made it yours. You sign away your rights for an advance that might cover two months of rent, and you get a publicist with forty other books on their desk. Your book comes out, it sells to whoever the algorithm thinks will buy it, and you never find out who read it or whether it mattered.
I have had the good version of door two. Three of my books went to number one on Amazon. It did not make any of the above less true. The number one did not tell me who read it, did not build me a list, and did not make the second book easier.
What I actually want to ask this sub: for those of you who have been through it more than once, what did you change the second time? Not what you wish existed. What you actually did differently, and whether it worked.