But Matic Network advertised on Bitcointalk for example. Solana has a short ANN thread created back in February. Not sure if the OP is a team member or just a supporter of the project. I think Tron advertised on the forum as well, but I could be wrong about that.
Matic made ANN thread, then one more post month after and never really came back, and it's been almost 2 years now. Cosmos, Tron and other few projects you mentioned are also not really new and are at least few years old. About decentralized VPN provider, you maybe mean Mysterium? At least that's the decentralized VPN provider that I heard of. So yeah, those are not exactly new projects at all, which I had in mind when I said that bitcointalk is not really place anymore to advertise altcoins. This can also be seen through decrease in post count, which was at its peak during last altcoin season.
But generally, I don't think that top altcoin projects even consider advertising here, as even if they do bounty campaign, I doubt that they will have much effect; if they decide to start signature campaign and pay in their tokens they will get bunch of shitposters, and if they create ANN thread it will be drowned in the pile of shitcoin threads.
To answer the OP, this forum will always have historic significance as it was created by Satoshi himself and despite all these new means of communication, will always be relevant when it comes to discussions about anything bitcoin related. After all, that's why this forum is created for.