Earlier quoted context omitted.
I also had fun making gold in Skyrim, which was offline. I don't recall it being work, but whatever.
It can be a puzzle with a built in score and fun, but rarely are these direct-to-cash games fun. D3 got much better when the real money auction house closed.
D3 RMAH was bad because D3 was bad. At that time there was basically no itemisation, everything gear was basically dps/main stat/trifecta. D3 was so bad that the fix was to remove trading completely and never been brought back.
People traded D2 items for gear, runes and/or real money for decades, there is no problem and the game is alive for well.