This made me realize why I found this whole question so confusing. I write code professionally, but don't really do open-source professionally or personally. There's just very little reason for two people to be writing code in the same file in the same week in my job. If it does happen, it still doesn't usually come close enough to cause a conflict. The rare case I find myself resolving merge conflicts is usually because I have some super old stash that I decide I actually want to apply months later.

Also having issues, pull requests, Projects and so on to organize work.

Are you suggesting you don't throw 5 developers simultaneously onto a new project with poorly defined and understood requirements and tell them to just get their story done whatever it takes? Because let me tell you, that is a recipe for merge conflicts...