"If a game has more than 40% day 1 retention, then it is doing really well."

Game Analytics released an interesting report about mobile gaming.

You can download it here: https://gameanalytics.com/resources/item/mobile-gaming-industry-analysis-2018

If your day 1 retention is low... If a game has low day 1 retention, then it’s probably going to need a massive overhaul. Many studios drop underperforming titles (sometimes killing games with anything less than 35%). Although this can be a hard decision to make, it’s sometimes better to cut losses and move on to the next project.