When he asked whether long time supporters would want to pay $30 bucks for the game I don't think that was implied? Seems fair to be annoyed.
https://www.bay12games.com/dwarves/ https://steamdb.info/app/975370/history/
DFHack already added back the keyboard cursor, anyway: https://docs.dfhack.org/en/stable/docs/tools/toggle-kbd-curs...
(I agree with your broader point that it's not reasonable to be angry at Bay12 for dropping this feature.)
Also it's not either or. If it is paid or free it's irrelevant. For example even if you pay, the seller doesn't owe you anything than what you paid for. And by contrast with totally free software we still file tickets and want things.
We can be frustrated by somebody's actions knowing we can't really demand something.