Adding content that doesn't match my interests without the option to skip / bypass / shortcut it
Removing content without reason
Nerfing a game / removing game mechanics "to make it interesting for casual gamers"
I join the "3-4 months" club. If the dev gives regular updates about progression and a longer waiting time is reasonable, I'm also patiently enough to wait longer. "Dev silence" is the worst. If a dev decides to abandon a game or doesn't have time to continue the development, he / she should say it.