Those are business problems, not tech shortcomings. Poor performance is due to horrendous overselling, while poor maintenance is due to being cheap.
You don't have to oversell like that. It doesn't change the fundamental, unavoidable fact that containers are a far more efficient way to virtualize than hypervisors for fundamental architectural reasons. An OpenVZ-based hoster that didn't oversell ridiculously would be cheaper and faster than a hypervisor-based host.
With a hypervisor you are running an entire kernel within a simulated machine within another kernel. That will never be more efficient.