When I was 20.
The squat had always been an exercise I could not do properly, I could never do a heavy full squat while maintaining the natural curvature of the lower back so I squatted as low as I could which was the half squat ( hip just below parallel) which was alway tricky when I used the maximum weight for low rep's.
when I was 35-40 there was a a lot of of talk on the internet about squatting ATG if you didn't squat ATG you weren't squatting, looking back I believe this to be true
After some time i realized the my body was unable to squat in the position I needed, the shape of my hip and my levers where the issue.
After reading and talking to some people I discovered that to address this I found doing Iso-lateral work on a leg-press was my alternative I was able to bend my knee really deep for the first time I could really feel the glute work, the glute has always been a weak point for me.