> I just wanted to mention to readers that even squatting a ‘measly’ 50KG or deadlifting 30KG
Yes -- this is really important to contextualize.
Barbell resistance training is actually two things:
1) A method of exercise that has a variety of well-quantified health benefits including improvements in strength, bone density, and connective tissue. More muscle also means you can eat more without getting fat.
2) A competitive strength sport (generally called powerlifting; weightlifting usually refers to the explosive overhead lifts seen at the Olympics).
Your strength goals can, and should, depend entirely on your objectives. If you're aiming to compete, a 150KG squat and 200KG deadlift would put you around the median in the lowest male weight classes.
If you just want to get in shape, it's overkill.
But maybe its different if you look at amateurs.
For me, bearing in mind all this injury discussion, I've focused on form 100%. When doing free weight exercises, this forces a whole bunch of other, secondary, "stabilization" muscles to some work. It's those, especially if they end up spending all day "locked" because of your posture, which can produce a lot of the minor pains of age, so give them a workout.
0. https://www.strengthlog.com/deadlift-strength-standards-kg/
For example the beginner on there is 76kg. I think it'd be a bad idea for a guy who's 40 years old, untrained and out of shape to rock up and deadlift 50kg, even just for one rep. He wouldn't know what to expect, he'd get the form wrong, he'd probably hurt his back. People who aren't trained should start with the bar, sometimes they're better off starting with even less than the bar and that is fine!
30kg DL is 5kg on each side of a 20kg bar which is less than I've lifted my very first time and I was pretty unfit and I'm sure the vast majority of untrained people can lift that. Hell, that's easier than bar-only bench press, which most people can also easily do on their first try.
* 20kg-30kg makes sense for an untrained person's first lift, it sounds like we agree. With DL you need some plates on the bar to get the right height so 5kg bumper plates or something is common.
* All of this is still way below the numbers even for beginners on the site you linked, which again I stress, is a self-selected group of people who were hardcore enough to opt into a performance tracking app of some kind, this is way different from the general population.
* I actually don't agree that the vast majority of people could just bust out, let's say, 10 reps at 30kg of any lift. Women and older men who have never lifted? I really doubt it. A year ago it was hard for me to do 10 body weight squats, no bar no nothing, and most of my middle aged friends who have never exercised are probably still in the same boat. 40% of the US is obese... I think this perspective is biased basically towards young men (lets say under 40).