You both make very good, cogent arguments ... and both have provided food for thought to me and everyone!

I doubt the OP knew what he was getting in for here!
BTW, I don't see bigotry or sarcasm in any posts here ... just differences of opinion ... and possibly some misunderstandings.
In terms of "Trends" in bikes I must say I see many riders, especially newer, younger, poorer and less experienced riders going with smaller bikes. Will they stay on a 125cc bike? Some will, some will move up. Remember, many never rode bikes before ... so would be dumb to start off on a R1200GS.
Guys with more experience and talent can handle a big bike, plenty of the old guard still out there on the road.

Part of (IMO) what is fueling this perceived shift to smaller bikes in one segment of riders is AGE.
For me, at 68, I no longer have the strength (or bottle) to handle a GS or KTM. I'm also too short and no longer willing to ride aggressive enough to make it through tough sections. If you don't attack it, it will beat you.
I did through my 30's 40's and 50's so I DO have experience on the big bikes.
GS, Vstrom Tigers, Capo Nord, Buell.
And as mentioned at great length ... both have advantages and disadvantages.
For new riders, experience is the best teacher. And, IMO, new riders SHOULD be starting out on small bikes ... then ... if they want to ... can move up to something bigger.
But for most doing long journeys are more often road rides as opposed to dirt rides. More adventurous folk will go off Piste and explore. For this, (for me) I prefer something I can lift and won't kill me if it falls on me. My DR650 is borderline OK ... off road I still have to be careful when she's loaded. So, many riders stay on road on big bikes. All good.