If you were introduced to Discord in a non-gaming-related context, it is very common to be unfamiliar with the tendency of gamers to share what game they are currently playing. There is no such habit in other, more "serious" contexts - for example MS Teams does not set "currently using Microsoft Powerpoint" or "currently coding in VS Code" as my publicly visible status at work. I can thus fully understand that a lot of people are (negatively) surprised by this - even gamers, because there's a huge number of people preferring singleplayer games out there that don't have the need to do any group coordination for which a tool like Discord (or built-in community features of games or game launchers) would be needed.

Hence if Discord aims at expanding its user base beyond the (multiplayer) gaming community, it should definitely think twice whether to keep this sharing setting enabled by default. At a minimum I would expect them to try to deduce somehow whether you are using Discord as a gamer or in a non-gaming-related setting, and use the suitable default. Or maybe just disable it by default, so gamers who want this feature enabled need to turn it on.