The same I see Bitcoingarden forum looks quiet visitors and only a few active posts today means this forum can not be compared with bitcointalk and obviously the difference is too striking.
While altcointalk seems to be filled with spammers and duplicate accounts, just visiting altcointalk there is a Hhampuz account fraudster by launching a freebitcoin signature campaign.

I'm sure one day they will find a good forum platform for mixer promotion.
I completely forgot about Bitcoingarden forum. I have account there, they used to send email newsletter once in month, but now I haven't noticed it for a while.
But other forums can't be seriously considered as alternative platforms for advertising. Look at Bitcoingarden forum - what's the point to advertise there when there isn't much activity. I don't even talk about Cryptotalk - it's completely dead spam forum, except Russian board where there is still some activity.