It will build quad muscle for sure, but that's about it. Squats are hard because they focus on so much more than just your quads--glutes, back, core, etc.--and, as
BPPLEE stated, it is more "functional," that is, it will help much more with natural movement. Having said that, there are quite a variety of squatting methods and while there are core bits of technique to keep in mind, there is some room for adjustment based on physiological differences.
Remember, body builders are looking for symmetry and size for every possible muscle, so they have to focus on a ton of isolation exercises, which isn't necessarily ideal or even necessary for the vast majority of people. However, leg extensions are better than nothing and if they work for you, do them.
Generally, less is more for the average person, which is where compound movements such as squats come in, with some relevant accessory exercises to benefit and support the compound lifts. Of course, it's really not either/or but both/and for optimal development.
You might know all this, so sorry if you do (hopefully it will be of benefit to someone).
For the record, I hate squats and suck at them, but I do them (quite irregularly, for health reasons) because of the overall benefit. I also workout at home, so some form of squat is all I have for quads. lol Personally, I would add in leg extensions if I was at a gym.