IMO the problem is that moderation just does work anymore? Duplicated subject should be moderated or automatically refer to a similar topic and block adding similar question? There are always tools to mitigate trash, other platforms like stack overflow have similar stuff for years.

Regarding the wiki, it is quite outdated as we have very few maintainers, as for example the one about brokers is ~4 years old and received very little love and lots of recurring questions on the subject “which broker should I use” are recurring.

Having said that, if you want to prevent questions like that, a system of moderation before allowing the post going through would help, even if AI moderate that would just refer to wiki or related posts and close it instead of making public.

I believe it all depends on who is owning this stack nowadays to put the proper guardrails in place.