I understand (as stated in the Steam Subscriber Agreement), that Valve does not have any such obligation to distribute workshop content. This is predominantly an issue as most mods are posted onto the Steam Workshop, which is the most popular distribution method for said mods. However, some games have this feature disabled, leading to said non-Steam games lacking any way to install mods from the Steam Workshop. The only alternative solution would be to use the Steam CMD console to fetch mods through an anonymous user / logged account. These mods could then be manually installed into games which were not featured on steam (Xbox Game Pass, GOG, Epic Games, etc). Previously, a tool named the 'Steam Workshop Downloader' was used to download mods (This was discontinued as per Valve's request).