Yobit can not be blamed for the low turn out of signature campaign it is just a coincidence that campaign are not coming out.
Also the 20post a day maximum can result to spamming and to add to that the simplicity to join the campaign with out proper screening of participants can make matter worse.
About altcoin it's not recently that high Ranking members started to see that altcoins campaign is turning out to be time wasting at times, and the newbies that are there some with multiple account on the same bounty are of the option of other campaigns like social media, article Etc. Still yobit is not to be blamed for that.
Also the manager that is handling the yobit campaign thread has compiled list of those wrong doers
https://bitcointalk.org/index.php?topic=5188200.0