Overwatch is removing two maps from the game completely

gamepur.com:

Right off the cuff of an announcement that Overwatch 2 would finally have an open beta soon, the original Overwatch game is still in a content drought, with the total removal of two maps. Fans might appreciate the loss of content in this case, however, as Activision Blizzard is removing two of the most controversial maps in the game: Horizon Lunar Colony and Paris.

These maps are leaving Quick Play “and other related modes,” giving the casual mode two fewer maps in its rotation. These maps have already left the game’s Competitive game mode, but now the 2CP veterans won’t even be available to the casual player. This doesn’t likely matter too much, as the Assault / 2CP gamemode was already leaving Overwatch 2.

Blizzard had previously attempted to “fix” Horizon Lunar Colony and the 2CP gamemode as a whole, giving the map and mode numerous tweaks and remakes to try and make it more competitive and balanced. Unfortunately, these numerous attempts failed, and the legacy of Assault maps is likely gone for good once Overwatch 2 drops.

You can read the official Patch Notes here, which details the change as well as fixes to the 6v6 Competitive Lockout Elimination mode.