Increasing Average Visit Length

My studio recently released our latest game Looting Simulator. On the 8th of June we spent 12K on sponsors over 4 days to collect some analytics. The average visit length seemed alright, averaging around 11-12 minutes. Yesterday we spent 15K on ads and 34K on sponsors over 2 days. Average visit length has now dipped down to around 10 minutes.

Ideally, our average visit length should be around 15 minutes, but we are unsure on how to achieve that. From our testing there are no major bugs or performance issues, so the problem must be due to gameplay. Please let us know if you have any feedback or solutions for us!

Do you have any daily quests for rewards
Time badges

Those could maybe up the average

Usually here’s the issue.
Simulators are mostly generic, boring and unoriginal, and I don’t see anything special with your game either, however, make new items cheap to buy so the players won’t be too desperate.