I suppose in the beginning of the decade, when crypto and bitcoin weren't well-known, bitcointalk was the hub to join in order to understand and innovate crypto... but back then the only people getting into bitcoin were coders, deep web enthusiasts, and some people who were bore. So it was very niche.
I think that the biggest problem here is that most of the topics there are focused on earning money through signature campaigns and bounties (posted by users whose post quality is terrible) or on complaining about merit which as far as I noticed, was introduced at the beginning of this year. I agree with the OP.
That's my point. The reason why the majority of beginners are into those kinds of threads, and posting about merit and sig campaigns, is because they're the new generation of "crypto enthusiasts" who are only joining bitcointalk because they think they can make a fast buck or some kind of quasi-passive income on forums.
There's no real way to change that. It's just the atmosphere of crypto right now. It used to be that the people joining crypto 10 years ago were computer specialists who were into the true philosophical mission of bitcoin... now it's just stay-at-home people who probably don't know what printf does in C.