When you start a new venture, you need to be very clear on what your exit strategy is: a viable business or a "disruptive technology" that you can sell. I will discuss the second one first because it is easier.
If you are building a "disruptive technology", the goal is eyeballs. You are trying to get someone to see what you are doing and make them think, "OMG, if we let these people go they are going to put us out of business". In reality, you are building a demo. It doesn't matter whether or not you get the details right. You can get many, many things wrong and it won't make a difference. Your goal is to be impressive and to have the potential to get it all right before anyone else can.
If you are trying to build a viable business, then ideally you want revenue. It is very important that you get the details exactly right, but at the same time you need to get revenue as soon as humanly possible. The way to achieve these seemingly opposing ends is to keep your scope as stupidly small as possible. Write something tiny and details oriented that will get revenue as soon as possible. Grow in very, very tiny increments, making sure to get the details right as much as you can. Make sure your revenue grows proportionately.
The common mistake is that startups often don't think about their endgame and their strategy realistically. So they say, "We'll build a business and disrupt the industry". This is highly unlikely to be successful because the disruption requires high risk manoeuvres where if you pay attention to detail you will be forever at your keyboard and never deliver. But building a business requires low risk iteration with attention to detail, so if you throw in "and nobody has ever done this before" then you will never get your first iteration out the door (or it will be so sloppy that you'll never get any revenue).
The reason that people don't realise this dichotomy is that the "unicorns" are companies that have often struck it rich, like the '49ers of old, by being lucky enough to be able to pick up gold off the ground. They break all the rules but are successful anyway. Do not attempt to replicate their success or you will become the toothless alcoholic sitting at the side of the road mumbling, "I coulda been a '49er".
You didn't read PG's essays [1] did you?