I still think there's a place for forums like cplusplus, even with AI.
I can trust AI to give me a summary of what's already mentioned in documentation and other forum posts but there's no substitute for asking someone who's actually tried an idea and knows whether something would work.
I personally haven't been as active because of work and because I've been trying stuff out on my own.
I've used reddit for cplusplus questions sometimes but it sucks at formatting code. Formatting is also sometimes buggy, especially with the carriage returns and stuff.
Stack overflow is useful only if I've stubbed code to demonstrate a problem, otherwise I get stoned for making a low-effort post.
There is a place for sure. That isn't the issue.
This one won't let new people join easily, something is broken there (?). Its also on the 'bad site' list people provide to beginners, because of the out of date c++ version over in the documents area. Between the two, you are up against learncpp which has up to date info and other forums that have more people and actually work when you join / post in them.
Its been a good home for a long time, but its demise is its own doing and was always just a matter of time.
Stackoverflow is so bad now I don't even go there for answers anymore. It used to at least be good for that, but the ham fisted admins have made it worthwhile to go anywhere else first, second, and third.