Let me make a guess, you are around 5'11" (180cm) and 175 lbs (80kg), or around average for a male? Because a "dining table chair", a universal product if there is one, is made for average sized humans.

It is funny though that Aeron is brought up as an example of a "universal" design: they are admittedly not universal since they offer 3 sizes (A, B and C). When looking at chairs, I've only went with their Embody because of the fluid back mobility it allows when sitting, though I still wonder if I should have gotten Aeron C (I always found it sad they did not continue with the practice of differently sized chairs with Embody which I love). I've also have a sit/stand desk that I switch between every day for the last ~10 years, but I've still developed back problems.

Why do I say all that — at 6'5" (195cm) I believe to have pretty strong core and legs, but I developed back problems when I got a kid (herniated discs, with a nerve getting pinched in the lumbar area recently). I live in a world where everything is too low for me, and I have to take an unergonomic position to achieve many things. Especially with kids (baby cots, strollers, they are really short, but everything, really).

A dining table chair has a seat length that generally allows me to only rest most of my bottom on it, but basically nothing of the thighs (which are also longer than average even for people my own height), which means that majority of my 90-100kg weight is concentrated on a small area. That hurts, so I have to move around and change the area under pressure.

I had to stop playing jumping sports (I jump around 30 inches/75cm high when not in regular exercise, so that's how far down I "fall" when going down) because impact on landing was too strong and it started hurting in my back. Yet after being in bed rest for 5 days for a pinched nerve, I went for physical therapy and could immediately hold plank position for >1 minute. "Your core is strong, so it is probably genetics", my physiotherapist would say. It's not only genetics, it is the fact that I am outside the design range for all the products that people use every day (I am probably among the 3% of largest humans and even the widest covering "universal" products cover from 5-95%: I can imagine very short people to have similar issues). I can barely find a car I can comfortably drive (if I push the seat back enough so my thighs rest on the seat instead of being in a squat, steering column will frequently not come out long enough, and my shoulders will hurt). I might fit in a Mercedes S-Class, but sorry, I can't afford it (though even that is designed for comfortable sitting in the back).

And I thought that's what the OP is about. Are you averagely sized, or do you maybe have some parts extra long or extra short? Or are your shoulders narrow or maybe extra wide (eg. I can imagine someone with very wide shoulders having more trouble with laptop keyboards)? Even the way our elbows and tendons connect is very different, so relative position of every limb could be taken into account to develop non-universal products.

I guess you have to find where you are "unusual" in your body constitution to really emphatise with the OP and how "universal" design is not the way to go when designing products for the physical world.

The same holds for the virtual world, but for some marginalized groups (at least in the past, like people with disabilities), legislation is required to make sure the basics are available to them. But generally, the market is ripe for less universal products.