There may be less R space, and so-called TODs (I've flown a lot too on my own dime, not enough for 1K or even Gold but enough, and I've never seen an international longhaul upgrade less than several hundred dollars offered).

But I'll accept on the face that those could be contributing factors. However back when I worked Reservations, when the IPTE planes started rolling out, we noticed a marked increase in complaints that upgrades were less available on those specific flights.

This was pre-merger, pre-3/3, pre-everything. The only measurable difference is that these aircraft had the new seats and therefore less inventory, paid or otherwise, that the same (or more because it was considered more desirable than the 'Barcaloungers') amount of people wanted to sit in. Your experience may truly only be different after 3/3, but I'd say there was already a growing undercurrent of unhappiness with less amount of upgrades, and 3/3 (yes, definitely many valid issues that to this day are really bad) gave many people a good scapegoat to blame.

Also, (and not saying you, but there are those out there) human beings often do have a propensity to exxagerate greatly. I have had my fair share of customers (both GS and 1K) calling and complaining that their system-wide upgrades were COMPLETELY useless because they NEVER EVER cleared. And I would politely point out that of their allotted 6 for the year they only had 2 left with 6 months to go because 4 had already cleared and been used.