Absolutely 100% spot on. And true of all software projects. There's a point where you fix the scope and the technologies and start work, and you only ever fix forward. Every project is difficult and has problems, but you fix them, you never switch horses mid race....Real game developers make basic design, build on it, possibly adding some tech if feasible that has been released between start of process and release point. But always there is some point where developers make decision: This is it, we are going to release this now. ...
You are also utterly ruthless with any scope creep. File them all under 'Phase 2'. Maintaining focus is key.
The is the big-picture reality of any development that stands a decent chance of success. I've never worked in game development, but I am a retired Programme and Projects Manager and have seen big projects that both worked and failed.