How welcome are non-space marine armies/players in your circles?

30k is always really big on Space Marine Legions and their Primarchs, which makes sense since they are the narrative focus, but it seems like anything non-astartes is almost unwelcome? Any post or mention of different players and their factions feels like it exclusively mentions different legions, and never touches on Admech, Emperor's Forces, or even Solar Auxilia (Even this sub's "Getting Started" post exclusively mentions legions) Would people in your play groups be disappointed/unenthused if it wasn't Space Marines vs Space Marines?