No hypervisor for cgroups (docker & friends), no. Which is why something like LXD/LXC outperforms hypervisor virtualization by quite a bit.
I was on a team that ran performance critical stuff for a reasonable sized ecommerce business - moving from vmware to bare metal was fantastic on every level from api’s to performance and reliability.
No, Docker is not a hypervisor and doesn't use one unless you need to add one for security reasons; it uses Linux features to build containers. On the other hand, yes switching from virtual machines to containers it is likely to be a non-trivial workflow change and not something a company can do on a dime.
