I think this would probably boil down to how much traffic each site generates, and your budget.
Discourse can absolutely do all of the above, but if you’re serving a ton of content to anonymous users on the WordPress site your cost per page view is significantly lower.
A $5 VPS configured correctly can serve millions of read-only page views pretty effortlessly, that’s where WordPress excels. The same traffic would need considerably more resources were it served via Discourse. WordPress is still an incredibly effective tool if you care about such stuff. Configured correctly it’s also pretty excellent for curating the content you serve up to search engines.
I have one customer who currently pays DO about $100/month for the two. When we investigated moving things wholesale to Discourse the running costs would have been an order of magnitude greater, it’s safe to say that piece of work didn’t go ahead.