I agree. But size is weight, and weight is size. Most animals house a close approximation on a cellular level to muscle mass/fat/blubber tissue. I think their carrying capacity represents this well without being too bogged down in the minutia.
I think that is one path they could go down. They seem to be breaking from grittier realism. I wouldn't mind it. I do have one caveat though: I think there should be a large section in the DM's Guide that specifically tailors rules like encumbrance and strength to a sword and sorcery style gameplay. In other words, a specific section that ditches the halfling wielding the two-handed sword and carrying double their body weight and gives them a max strength of (fill in the blank). I don't think I would ever use these rules, but I know many that would. And I feel it is only fair to include those players as well.
When 2024 rules disentangle Strength Athletics from Strength Weightlifting, it will be far easier to utilize and describe one without the other. Thus there can be a low Strength Athletics "lumbering Giant" versus a high Strength Athletics "pouncing Panther", even a high Strength Athletics Rabbit.
Meanwhile Size and Weightlifting skill quantify brute force separately.
Then a "gritty" genre variant in the DMs Guide can detail some ways to keep Small "small".
Those small and tiny creatures do not have extreme strength. They have an athletic ability. If we used the old stop the frost giant from breaking through the door scenario, no matter your athletics, no 30-pound creature would stand a chance against a 400-to-500-hundred-pound creature. But in D&D - they can. And that is okay.
I did the math.
According to D&D 5e Monster Manual, a Frost Giant is about 21 feet tall, and has humanlike proportions. Therefore:
• Frost Giant with Swimmers Build weighs around: 7,187 pounds
• Frost Giant with Bodybuilder Build weighs around: 9,261 pounds
If this Giant tries to kick thru a door, there are many tons of force. Unless the smaller creatures are using magic, there is no resisting this force. Of course, the door itself might be structurally reinforced, but then the smaller creatures wont be adding much to its resistance.
Because height is a linear length and weight is a cubic volume, when two creatures have the same body proportions, the one that is twice the size is eight-times the weight.
So, a 3-foot Halfling has about an eighth of the body mass of a 6-foot Human.
What I am saying is, D&D is unrealistic, and in the modern version, it is unrealistic to the extreme. And that is okay. But, there should also be a space for those that want a more realistic D&D.
But neither the halfling nor the dwarf are magical. And there is no explanation for the halfling to house an innate strength much greater than its weight. Except that D&D wants to use loose and vague terms. And again, that is okay.
I basically agree.
My contention is, what you characterize as "unrealistic" fantastical exaggeration, is what I characterize as by definition "magic".
But it is innate magic − not the kind of magic that is manipulated by formulaic words. In other words, the power source is psionic or primal, rather than arcane or divine.
And it is explained ad nauseum why Superman can do this. In fact, he is one of the few that can. And it puts a worldwide spotlight on him because he can. In fact, it is so rare, that less than .0001% can accomplish a fraction of his abilities. But this goes to my original point in my last point. D&D is purposefully vague. It is good they are vague. Otherwise, it would break immersion too easily.
Re Superman as defacto magic. Even if a "sufficiently advanced" technology, it is still a D&D magic power source.
Notably, nothing about Superman feels like the arcane power source or the divine power source. Superman might be the psionic power source, like his son is. To me Superman feels like the primal power source. He is a manifestation of the four elements: fiery laser beam eyes, watery icy breath, airy flight, and earthy "man of steel". Thus, like other nature beings, he is an innate caster of the primal power source who wills his elemental manifestation into existence.