There is no excuse not to squat but if you have a bad back or knees you get a pass, follow the trainer principles to blow up your quads.
On the leg press go all the way down and back up without locking out until you feel the burn then pause for 2 sec without locking out and crunch out an extra two reps. 20-25 reps dont go below 15 reps.
On the hack squats go all the way down and back up to slightly above parallel no lockout and feel the burn 15 to 20 reps.
Your quads should be fried like chicken.