Right. I've done squats with something under my heals, which certainly helps deal with the leaning issue, but still makes the knees wobbly when you go heavy. Again, the issue with squats is it become almost a total body movement, loading several levers that cause more total fatigue; spending energy on stabilizing rather than focusing targeting specific muscles for hypertrophy.
I do leg press with full ROM: my legs open up and my knees go deeeep as far as I can possible go, unlike many who load up the rack, and do half reps thinking they are doing it right.
I will do some squats on the smith machine, as I did today, but I feel they are suboptimal, probably because my gym only has the diagonal smith machine, rather than the one that is straight up an down.