Agreed, it'll depend on the team and your own preferences, and the amount of time you can commit, and your level of experience.
I'm not an expert, but here's a top-of-my-mind, napkin-sketch framework to think about.
(Some of these may overlap)
-> Team meeting (comms, responsibilities) (2 hours) (figure out how you'll communicate, how often, who does what, and how much is expected.)
-> Ideation (1-2 days) (It's vitally important to get everyone onboard with the premise, or you'll lose people along the way.)
-> Infrastructure (Engine, Git, etc) (<1 day) (Is everyone familiar with the game engine and version control? Who will act as the steward of the main branch?)
-> Rapid Prototype (2-3 days) (Don't worry about architecture, just get something working. Worst case scenario, you can publish this if everything goes sideways after this.)
-> Refactoring (1 week) (Now you worry about architecture, coding standards, folder hierarchies, etc.)
-> Bugfixing (1 week) (Always more bugs than you think. Tackle the hardest ones first.)
-> Polishing (1 week) (Takes longer than expected. You should have a UI, theme, menu system, levels, add juice, then add more juice)
-> Publishing (1-2 days, but start early) (export and test, export and test. deployment usually takes longer than you think.)
-> Marketing (2 days) (someone makes a trailer and makes the page look nice on Itch.io. Hallmarks of quality, often overlooked.)
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Side note: It's common for teammates to wait until they get a request for assets. There's no reason to wait. Everyone should be producing something all the time, (time-permitting).