in some way i agree with you. Knowing when to fold´em and when to hold´em is the most basic and fundamental part of the game, specially if you´re a newbie. That´s the reason why the bad players are classified as the ones who enter in all the
hands and call every bet. And that´s why when you´re starting to play the game it´s recommended to raise 5 or 6 times the BB preflop, because with that strategie the newbies will learn the value of the hands, and they will learn that if they play all the hands (wich most of it is crap), they will lose more money than they win (of course then they will learn that the common bet preflop is 3 or 4 times BB).
That´s for newbies, and i think that it´s still the most basic thing for every kind of player (begginer, medium, advance, expert, etc.), but when you "reach the new level" i think that everything matters for equal. If you want to play a winning, solid poker, you have to pay attention to every detail, like the position, your opponent playing style, his
tells, your stack size, your opponent stack size, playing with your opponents hands (thinking of what they could have), etc. And of course the
odds are very important. The winning poker is a mix between skills and math. If you think that knowing when to fold is important, that´s because the odds are telling you not to go, because most of the time your hand is gonna lose. Howard Lederer told me that the most important part of poker was math.