Autoplay treasures can be undone without approval from opponent, which is nice.
However, I was in a game where my opponent repeatedly autoplayed treasures and undid that, which evidently resets the clock for forcing resignation. Thus the opponent can keep doing this to stay active, but the game never progresses, and the only alternative to sticking out the battle of patience is to resign.
If that happens to you, resign the game and report the player at
https://tinyurl.com/dominion-abuse
This posting (https://forum.shuffleit.nl/index.php?topic=4554.0) on this forum gives a little more context to that process.