This. Statistics and probability? Yep, they're most likely needed, though it's more of actually memorizing the cards that are possible for you to lose against while pairing up with the cards the dealer has already placed. That's just determining your odds though, and it's not like you can always fold when your cards are bad, or heck even at the middle range good cards. Bluffing is needed to guarantee a win in those cases, since it adds what @betwrong said, unpredictability.
Statistics and probability aren't on the realm of what the player can control so I don't think that it isn't really needed, you are right about memorizing the cards since a process of elimination is going to help you deduce the possibility but you are only limited to your cards and the cards shown by the dealer. Bluffing is good but you don't have to look like a try hard doing it because they pros will see through you when you are bluffing way too hard.
Memorizing the cards will not easy to do, especially if a person that can not memorize them. Not many people can learn about poker, but they can learn more details about the game. They can also learn about how to bluff the opponent to have a chance to win. But that will be difficult if their opponent will have more skills than them because their chance to win will not be bigger. But I think if they can often to playing poker game, sooner or later, they can try to bluff and memorize the card of the opponent