One of the most useful tidbits of knowledge I’ve ever discovered was where the true weakness is with my squatting. I am a generally weak squatter to begin with (I like to blame my rusty, rebuilt zombie knee, but it started long before that) and my deadlift gains are consistently outpacing my squat gains.
With my feeble attempts at squatting, I’d often get folded over into the dreaded squat-morning, and after intense blocks of training I’d feel tight in the lower back. This is a fairly common issue for a lot of younger lifters, and its almost always misdiagnosed by the young lifter as a weak back. Why else would one fail to maintain food bracing and good posture, right? The real answer is the dominance of the posterior chain, and weak legs. You may not consciously know it, but your brain is telling you to “run away” from your weak legs and rely on the strong point of your posterior chain and back.
Chad Wesley Smith and Max Aita of Juggernaut Training Systems discuss leg strength versus back strength as it applies to the squat.
And for other back strong/leg weak squatters, some other viewpoints for developing leg strength.
Leg Strength Workout from Jeff Cavaliere of Athlean-X
How to Grow Huge Legs, from Elliott Hulse’s Strength Camp
3 Easy Tips for Big Quads Fast, from Buff Dudes