It's a move toward CC and away from mid & low-tier elites
The fundamental change that's going on is a move away from flying-earned benefits and towards credit cards. Chase is in the driver's seat... we don't know how much money UA gets from Chase, but I have a strong feeling that it's Chase that's kept UA afloat during the dark years, and it's Chase that pads their bottom line during good years.
And the bleaker the benefits for elites, the better things look for the Chase CC holder. Free checked bag. UC access for an MP card that costs less per year than buying UC access outright, and provides 1.5 miles/dollar spent. Anywhere (2 miles/$ on UA.com spend). Priority boarding that puts you right up there with a 1P. What's left for the elite? E+ and upgrades, although upgrades are tougher to come by for any but 1Ks. Better service during irrops, but nobody pays much attention to that.
It could be that the RDM squeeze at UA's end is part of a deliberate move to make Chase CC cards look more desirable.
In the end, I just don't see the RDM squeeze from UA as being nearly as significant as fewer upgrades, loss of baggage allowances for some, reduction in E+ availability for the lowly 2P, etc. Perhaps most-importantly, I don't think the RDM squeeze will have any effect on the high-value-flyer that UA, and every other airline, seeks. But it will do away with the person who manages to find that rare opportunity to mileage run for RDMs (not PQMs). The new schedule will make ultra-cheap-fare RDM earning meaningless. And it may dissuade some from seeking a miles-based upgrade using the rationale that the RDMs earned from the trip offset a good percentage of the RDMs needed for the upgrade.
I have yet to see a change enacted or proposed by United that catches me off guard such that I'm thinking hey, I've really been given the shaft here. I don't feel good about many of the changes (I used to get more upgrades as a 1P than I do as a Plat, for example), but at the time time, I don't feel like I've earned more either.
What makes me happy? E+. Smiling crew. Clean planes. Efficient boarding. Making connections. Award tickets that carry my Plat status when I use them for others. Earning RDMs on business purchases with my CC. Reasonable PQM opportunities/maximization.
Earning RDMs while flying is way, way, way down on the list.