Wordpress divides posts + comments into 4 tables.
> which could be loaded asynchronously via Ajax for swift loading time and less load on the server (no slow view renders)
Wordpress can't assume any particular PHP + webserver configuration. Sometimes they're configured to send while rendering, sometimes the whole process blocks until it runs to completion. Ajax doesn't magically change that.
I also dislike the idea that I should need to download what is a small application to assemble a document ... when I could just download the document straight up.
When page loads get too long, I switch on pagination.
> cached with Nginx/Varnish, and further cached on the backend with Redis
My own setup is memcache for working objects. WP-supercache is configured to write gzip'd pages to disk and nginx is configured to serve .gz versions of page directly from disk whenever they're found. The OS file cache does the rest.
> I've seen WP sites that I had to debug/fix with 200+ queries per page.
When you see hundreds of queries per page, check your plugins and widgets. Wordpress is not my favourite software by any measure, but out of the box it's not that dumb.