I heard that in 2017-2018 was the best years since many people can earn a lot money with minimal effort, they only need to tweet, re-post, translating using google translator, spamming 1-2 liner(s) in this forum etc.
After most bounties turns scam, most people leave the forum, many users shift to signature campaigns and the forum still renting the ads banner.
Theymos decide to stop the ads banner, now starting this year the forum ban mixer promotions which make the traffic going down.
How to make Bitcointalk become popular again? enlarge and expand the incentives.
That of great, I precisely joined in 2017 and what I remember is that it was good times for spammers and scammers. I would say that the best time was until not long ago, since CM fell and there were several mixers who had signature campaigns on the forum. As we already had the merit system for several years by then, there was a mix of traffic, good contributions and a democratization in good campaign payments (before there was a huge difference between what CM paid and what the rest paid).
I don't think there is anything we can do. The mixers are not coming back, the forums are becoming less and less popular, and the only way that would be to attract a lot of good paying advertisers I see as unlikely. Add to that the fact that casinos, which are the big advertisers now, are in a kind of legal vacuum that I don't think will last for many years.