There is no perfect process. I think after a long time working in software I now understand that it works like this: you need one person to work by themselves really really quickly to ship and create the foundations. After that, they need to remain in place to make sure the design continues to make sense as more people add code to the monolith. Having a specification process is a must in complex environments, and the downside is that it adds friction (and some people can abuse the back and forth to prevent you from landing your design changes), so you need that process to happen as late as possible. But if you're running in production in sensible environments then you will need to make that process happen earlier than desired.

> you need one person to work by themselves really really quickly to ship and create the foundations

This is literally the secret of every successful project I've worked on. An individual, with high agency and low communication overhead has either been trusted to take the task on themselves, or they've done it secretly to side-step the approval process and organisational overhead. When the foundations are in place it's relatively easy to add engineers, but starting something from scratch with a bunch of people? doomed before it starts in most cases imo