My share . . more a written ejaculation, or a core dump if you will.
Really good input and real world results. That is what we need more of.
Squats.
Compound leg exercises are unique and very very individual primarily
because you must take into consideration rotation around 3 axis's of rotation,
and connecting each axis of rotation is a lever arm that has a different
range of motion and strength. That is why some can squat like a king and
some like a peasant.
Other exercises are not that difficult (relative) to perform / figure out.
Curls, calf raises, lateral raises, wrist curls, triceps extensions, leg
extensions, etc. All one axis of rotation. Presses could arguably consider
2 rotations but the difference if so minor as to be insignificant in my opinion.
All bodybuilding exercises and results come down to axis of rotation (single
or multiple) and the lever arm. Easier to find the exercise, then all you
have to contend with is speed of movement, sets, reps, and frequency.
Easy peasy.
If you are one of the lucky ones that can perform squats well and the
muscular growth is commensurate with the weight and you suffer no
injuries (now) that is why you are one of the lucky one. Most are not.
That is not to say that over time will prove you to be invincible (you
are not) it will just take longer to show up. Maybe the lucky ones
are the to ones that take less muscle to perform but with less inherent
risks. I don't have an answer for that or anything else for that matter.
Just some observations, self experimentation and outright mutilation.
That is why hacks, leg presses, etc., were invented . . . the reasons stated
above and the undeniable fact that they are the hardest exercises and most
result producing exercise known to man when properly performed . . .
which is rare. (Some here got straight A's in that class and it shows.)
I really dig what what Big Dave and Hawkmoon said about squats. And I
dig what others have said about the alternatives to squats, and their
observations about which piece of equipment 'feels' right. That right
there shows you how complicated multi-joint exercises are and there is
no one size fits all. But when you find it you are golden and the rest is up
to you. Hard work, And that comes disguised in overalls, aka, hard work.