just because something is your reality doesnt make it objective truth
Squats are bad for your knees and back....If you're noob trying to jump into the deep end with weights and shyt.. It's also bad if you're a strongman lifter constantly pushing past human limitations for years. All them nikkas end up with debilitating nerve , back, and joint issues eventually . Your joints dont give a fukk about ambition, mental toguhness, and breaking PRs. Dont ever go to this extreme. Stay within reason.
However
Legs are designed for generating explosive power and are the key to having proper body mechanics
Far as lower back pain, if you've been half assing, infrequently training legs or avoiding leg most of your life , you got damn right you will have lower back pain, It's a promise you will have back pain.
a solid , well developed posterior chain ( Back + Legs) is the barometer of for great body mechanics.
your knees and back hurt because your have weak, underdeveloped glutes(ass) and quads which means the hurt areas are overcompensating to distribute the heavy loads you place upon it.
you cant power through it,
you have to start from scratch, Body Weights --> Light weight --> Heavy Squats.
Starting out: Sumo Squats, Leg raises, glute bridges, pull ups, burpees will get you a solid, strong foundation
bascially anything them Bar Starz nikkas do