There is no other forum like bitcointalk because Satoshi himself was the one who created this forum in order for people to learn and spread the knowledge of bitcoin.
I know of one altcoinstalks forum, but from the name the forum talks more about altcoins without a direct knowledge on a specific coin. In fact, the forum was a mess and lacks good information before forum members here went there to add value to the forum. I believe that if Theymos lift up the ban from mixers, altcoinstalks will become a grave yard with less traffic compared to this present time.
Yes, I also saw all the mixer ads on the AltcoinTalks forum. And when I looked at the history of the BitcoinTalk forum, I saw that mixers were once promoted here. And now everyone has moved to Altcoins due to the ban.
Personally, I think crypto is discussed as seriously as it is in this forum. It is not done in other forums. So like everyone else, I think this forum is more than enough to really talk about crypto.