Maintaining a game after post-production is often called LiveOps. Now, whenever something new is added, there is great chance of something else to break. But the vicous cycle of fixing all broken parts after every new update is often infinite. Yes, adding features is a greater priority, but the more variables a game has the more difficult it gets to both balance and fix bugs. Only totally game breaking bugs/exploits are fixed immediately others are left as they are for later. I recommend a video called 'Thirty Million Line problem' by Casey Muratori. Explains the broken state of software we use nowadays beautifully.