The smaller amount of signature campaigns on the forum nowadays is probably due to the organizations running campaigns analyzing the benefits of both signature and social media campaigns and coming to the conclusion that social media campaigns are more effective, though it's impossible to know for sure and it could just be ICOs and newer projects trying to cut down on costs wherever possible.
I can't point you directly towards one campaign that's the 'best' either, since that's entirely subjective, but the
Altcoin Bounties is your best bet for altcoin-based campaigns. If you're looking for fresh campaigns, look for threads with few posts.
i have also observe the point op just raised with most project lunching their campaigns lately, majority don't have signature among as part of their campaign, i use to wonder why the exclusion of signature campaign but from your point of view, i think this could be one of the reason, there maybe others but i guess this is one major reason,
if the signature campaign don't bring the desired result as social media and content, then i guess most project would rather exclude signature from their campaign,
another possibility could be the bounty pool, if the pool is not very big, they will rather spend it on the campaign that can reach wider audience which is social media and content campaign.