Mistress Choi,
Squats were my forte back in my heyday. A knee injury from an aerobic marathon ended them for me. Now it's hacks and occasional leg presses.
If you want to really stimulate your quads, try pre exhausting them by doing extensions to positive failure followed immediately by squats with no rest in between. Reps are slow and controlled with no pause at the top of the squats. You'll really feel these.
If you want to get a little crazy try a tri set. Leg presses to one rep before positive failure, leg extensions to failure, then squats. No rest in between. You'll be huffing and puffing. Make sure your knees are warmed up before doing these.
See you soon.
Ray