Squats, SLDLs, and calf-raises are the only leg work I do. [/quote]
and this is where your problem is.
I do squats, deads (or GMs or lunges), pull-throughs, glute ham raises, all in one workout. You have to work on the weak muscle groups or you’ll be stagnant forever. Practicing only the full squat or deadlift in a training week is only good for
a) people built for the lift. They don’t need a lot of assistance work in order to progress.
b) people trying to build on motor learning principles to increase strength via CNS coordination and firing patterns.
c) people who’s main goal isn’t to squat more.
Sample workouts from my past, when I was much weaker:
squat, deadlift, lunge, bulgarian squat
squat, front squat, step ups, pull throughs
deadlift, front squat, pull throughs glut ham raises
box squats, deadlifts, lunges, back raises, bulgarian squats.
front squats, lunges, single leg squats, bulgarian squats.
I did 4-5 movements, with at least 2 being heavy compound exercises. The others were for weak muscle groups or hypertrophy.
Do more work. You’ll get stronger.