Limited actions on specific days, poor navigation, empty maps with nothing to do....
And then there are also the ones that have really stupid things like: Go to the garage, open the second box from the right on the shelf that's in the back, get the old coffee pot but leave the car keys in there. When all the mission/quest asked you to do, was to get "a container for water", without any hints for what kind of container or where to find it in the first place.
What the problem is with all this?
1. Asking for a specific item without specifically mentioning what, but referring to it in a much broad sense that could also apply to other things (like the long drink glass you had to get for another quest).
2. Lack of hints where the item might be found, and with 20 locations to visit and many more cupboards, boxes, under the beds and whatnots within those visitable locations, this is just a tedious timesink, no fun at all.
3. Oh, those car keys? If you grab them, 5 days later, your in-game dad will be angry that you stole them and kick you out of the house, resulting in a sudden game over, and you'll have to go many saves back to fix that.
Just some examples of really bad gameplay some developers put into sandbox games. Sandbox games need a LOT of consideration to actually be fun to play.
-Lots of content everywhere, idealy with variable random encounters that are not necessary to progress any of the storylines (but may be triggered by storylines or cut off at some point due to storyline progression).
-Very elaborate quest descriptions and/or quest hint system.