I cannot comment on UA (have not flown them in many years), but with changes to FF programs, I'm not surprised UA and DL made the list.

As I live abroad at the moment, many of DL's changes do not impact me, although they will when I return to the USA.

The change in earning RDMs will mean I earn 40-60% of what I earned on previous flights. That said, with ex-Europe fees on redemptions, the difference between booking an award with fees and just buying a ticket is not all that far apart. I tend to use miles for friends and family to meet somewhere in the USA or bring them to Europe.