Squats are not as "essential" as most lifters tend shove down your throat. Squats are great for building a base in a beginner to intermediate but once you reach a certain level, squats are not gonna build your quads anymore. Why? Because squats are a terrible quad ISOLATION movement. Squatting involves glutes, hams, calves, lower back, along with quads. All those muscles being worked puts a huge demand for oxygen in the body. So usually what happens is your cardio fails before your quads actually do. IMO leg press Isolates the quads much better.
But I'm talking strictly from a bodybuilding point of view. Of course if your goals are different then it's a different story.