Having young kids, my back, my knees and generally most of my body is/are in poor state. Having kids is a young man sport...
Several month ago, as I was going down a rocky muddy path (old Monarch's way), despite the 50-584 @ 28psi, the vibrations transferred through my arm locked my lumbars. I stopped rest and then carried on. As I got home, I ordered a redshift stem and since then, I have rarely experienced such discomfort (except when I first fitted the G-One ultrabite with 28psi - now 22/20psi).
A friend (15yrs older than me) experienced back pain too and added a redshift stem which helps a lot too.
As per the other thread, manufacturers are introducing suspensions to their ranges because there is a market for comfort and as seen with ortho implant, the population aged but still want to remain active so, equipment has to be somewhat performant but also comfortable.
Most of riders know they will not win the "Paris Roubaix" so they don't need super stiff performant machines, a good versatile bike which trades some performances for comforts allowing people to keep riding is a good thing.
So if people like gravel, single tracks, whatever terrain, rather than giving up because of some body limitations, customizing the equipment for their need is a good thing. Afterall, it is what people do with golf, car racing etc. so maybe be bike fitting should also consider that rather than just the position.