> I’ve seen plenty of people that are okay with picking up a codebase someone else wrote and working with the patterns and architecture in there BUT when it comes to them either needing to create new mechanisms in it or create an entirely new project/repo it’s like they hit a wall - part of it probably being friction, part not being familiar with it, as well as other reasons.

For me, it's exactly the opposite:

I love to build things from "nothing" (if I had the possibility, I would even like to write my own kernel that is written in a novel programming language developed by me :-) ).

On the other hand, when I pick up someone else's codebase, I nearly always (if it was not written by some insanely smart programmer) immediately find it badly written. In nearly al cases I tend to be right in my judgements (my boss agrees), but I am very sensitive to bad code, and often ask myself how the programmer who wrote the original code did not yet commit seppuku, considering how much of a shame the code is.

Thus: you can in my opinion only enjoy picking up a codebase someone else wrote if you are incredibly tolerant of bad code.