I have the same problem, and it really hurts the game imo.
You could make the cursors slightly change their sprite over active areas. Or add a label in a small font at the bottom of the top half that shows at least the name of the hotspot.
(The cursor images themselves are also a problem; I know the order and was able to determine what each cursor does but I wouldn't want to play this game as somebody without knowing about the classic Sierra interface. Yes, the readme mentions them. Still.)