So its essentially modders are only uploading their mods to the steam workshop and the versions of the game without workshop support are up shit creek without a paddle.

I admit I’m kind of guilty of this with the mods that I create and publish for stellaris. I pretty much only publish them to steam although Im given the option to upload to the paradox launcher. Personally I’d prefer to only publish through the workshop since Im used to the system, and its an easy way to get feedback on my creatons, however I can see the benefits to the ecosystem as a whole by allowing anyone who has the game to get the same mods in a bespoke mod store.