> have always refined features as part of the natural flow.

"natural" as in "law of nature"? Or is it just a process which crystallized in the course of your career as something which makes sense to do?

Scrum, and other methodologies are mostly a collection of such processes which proved to be useful, are somewhat standardized for learning and communication.

One can reinvent many of the Scrum processes independently, but I kinda don't see the point. Just like I'd rather use a finished library / framework rather than try to hack together my own.

No, but I believe that whatever you're doing resembles what is done in scrum. Gather information, discuss with your colleagues, create a plan. Scrum enforces that colleagues talk to each other, which I learned is not always the case.