At one point if you want to define what mean to master X, you would need first to know what is your objective:
- some people want to always explore, try to find things that nobody else did/things they don't know. By doing it, you can regularly ruin games by doing things others players don't understand/don't trust, even if it is optimal. The main upside is you improving over time since you often are one step further.
- some people play to have something similar to winstreak ("complexity cost"): to do that, you need at one point to said to yourself that things became too complicated and decide to not do them, even if you know they would be better, the risk of doing a clue that a single player on the table missinterpret can cause 2 bombs (mainly if another thing is going on, and a player do something unexpected from it). Some players will try to have the highest winrate, while others would do that in specific time (winstreak) which let them relax a lot more when nothing else is going on.
This require to be able to concentrate and rarely make (simple) mistakes.
- some people learn to be good at interpreting clues from new players/new situations. It make you lower the trust of every player, but make you instead think about probabilities of you having anything. Per example, you can assume that your next player know he has play in 80% of the cases. Knowing that, depending of the situation, you can do the best action which follow (if your next player got a 5 in chop, if you are in those 20% remaining, that's bad). This skill can be used too when an error is occuring during a game. You need to resynchronise the team, and to do it, you are forced to check differents possible state of the game for every player.
You can sometimes have a middle ground where you got defined conventions, but those one give lots of liberty of how to play them.
- some people learn to play with weird variants.
- some people saw that hat guessing exist, and lose interest on playing the game normally.
And just to put that here: better conventions (out of hat-guessing) seem to give clues which doesn't touch the card you want them to play: it give not only a play, but information on the other card of the hand.