This is false actually, it was Warcraft that was initially intended as a Warhammer Fantasy game then got swapped into something original. Starcraft started as a space vampire game and then gradually shifted towards what it became. Most dev interviews regarding SC1 also seem to indicate very little intentional connection between it and 40k, (like some dev members have gone on record saying they didn't know about it until years after, although others like Metzen played it at the time) but SC2 had several devs who had previously worked on 40k so at that point the overlap became much stronger. Frankly most of the similarities between SC1 and 40k are very surface level besides, and things which are all very common sci-fi concepts that predated both series.

For non-chuddy Warhammer spaces, Sigmarxism on Lemmygrad exists but is very barren right now. Sigmarxism on reddit is very lib nowadays but used to be pretty good and still has a few members holding out. Beyond those explicit lefty spaces hobby spaces tend to be far better compared to meme or lore ones. If you're willing to look into the other (and best) warhammer setting, Age of Sigmar spaces are usually far better since there's no Imperium and by extension it lacks the fascism it breeds in the fandom. Warhammer Fantasy ones are worse though.