You joined Bitcointalk in late 2017, and you think the current state is worse? Bruh. If you think threads right now are rubbish, what more in late 2017? I'd say Bitcointalk's current state is great compared to the past as a lot of people stopped due to the merit system and a lot of people capitulated due to bitcoin's drop in price.
The worst period of the forum is in late of 2017 that triggered the very serious action of theymos. From that we have, restricted boards and the merit system - that was also improved to derank old-era Junior members to newbies if they did not earn a single merit.
All of them, especially the merit system help the forum to become better and there are less rubbish posts than before.
Bitcoin's rises and falls are correlated with posting in the forum. It is especially right if we look at rubbish posters. ICOs and IEOs die out and their income from posting decreases to nearly zero, so they stop posting rubbish.