That's an interesting question and I'm going to give you a somewhat snarky but truthful answer: Software mastery is exhibited by the code that I wrote today - and oh how horrible it is to look at what I wrote six months ago.
Through-out my career, which is now over four decades if you include the software I wrote as a teenager (before I got paid to do it), I've continuously found a better, more elegant (which can almost always be read simpler or clearer) way to tell the computer what to do.
So my non-snarky view-point is that there's no such thing as mastery but rather that it's the proverbial journey. There is however a baseline at the other end ... if it's not functional and maintainable, there's a definite lack of mastery.
More likely that you a) overrate the quality of the code you wrote today (recency bias) and/or b) have forgotten the context/constraints that you wrote the code 6 months ago under
Through-out my career, which is now over four decades if you include the software I wrote as a teenager (before I got paid to do it), I've continuously found a better, more elegant (which can almost always be read simpler or clearer) way to tell the computer what to do.
So my non-snarky view-point is that there's no such thing as mastery but rather that it's the proverbial journey. There is however a baseline at the other end ... if it's not functional and maintainable, there's a definite lack of mastery.