In that context, you should become able to beat Noble regularly on fully random settings. At that stage imo you're in good shape and well set for Prince. If you can do the same on Prince, you've probably mastered the major threads of the game, and how they inter-relate.
Up to Chieftain, you can react and win. Eg Alex attacks you, you'll have time to scratch a defense together and beat him off. Or you meet Mansa from the other continent and he's miles ahead on tech--you'll be able to focus and catch up.
At Noble and Prince, reacting won't cut it--you need to anticipate to win. So you must maintain a certain level of military, economy and research "just because" to be competitive.
Monarch I've found is where you start getting punished for execution errors, like my favorites of forgetting to change civics, or to switch a specialist back on, or leave my fishing boats undefended for 'just one more turn'
I've only won at Emperor when I've played most of the game before making a move. Ie, a careful analysis of my circumstances, and some rough plans to capitalize on my strengths and minimize my downsides. Obviously refined and changed as the saga unfolds, but always focused.
So that's how I see it break down:
* React - up to Chieftain;
* Anticipate - Noble & Prince;
* Accuracy - Monarch;
* Focus - Emperor and above.
I personally don't like the focus constraint much, so I play mostly in the Noble to Monarch band where there's more than one way to skin a cat--but you must keep your knife sharp. Emperor for me is more like bathing the cat