Wow.. So I work with Wordpress on a day to day basis as well and we don't see anything like this.. We have pretty DB-heavy sites (lots of ACF Pro fields and lots of relationships) and we're handling bigger loads than that, on much smaller virtual hardware..
I'm not making any specific value statement about your setup here, I'm just surprised by what you're seeing on your end.
It could just as well be our ACF+CPT fuckery that leads to this – I'm not that involved in the actual application side of things; I just provision the hardware and OS stack.
Still, we're usually seeing a lot better performance with everything that's not wordpress – be it our in-house PHP framework, or node, Rails or Python apps.
Opcache is enabled, SSDs are in hardware raid and the whole time is spent inside PHP, MySQL finishes all queries after 0.02 seconds. The usual suspects are all dealt with.
I'm not making any specific value statement about your setup here, I'm just surprised by what you're seeing on your end.