Believe it or not, It's no longer a necessity to have a bitcointalk announcement thread. I feel this is so because 90% of the ann threads created between 2016-2018 have been long forgotten. The startups have gotten their funds and forgotten about it. See projects like Blox (previously Coindash), Storm, Mobilego, Effect.ai and a host of others. So I don't see it as a necessity since these threads will become ghostlands with no updates. But It's a good move if you would still create it. At least, the community can make a first impression about it and hear each other's opinions about the project's mission and relevancy in this already crowded space.
On the marketing side, it is essential for me, Bitcointalk is a very popular forum, people can see the information about the project and search engine will index the thread making it easy for would-be investors to know more about the project if past projects did not update their thread could be because they are now scam site, those stable coins that have a thread are still active here, if you are marketing your project, every place has a potential.