Yeesh, no wonder it's slow. I'm running proxmox on a Qotom "firewall appliance" with a 2.1GHz 8-core Atom processor with the most basic VGA output (and no audio), and my interactive Windows VMs are slow on that. Text-based and Linux instances are fine tho.
I'd say upgrade to a better CPU and better SSD if you want decently reliable speed out of it. The Qotom was a steal at 4x10Gbit ports and 5x2.5Gbit ports for under $400, but I have to keep it at kernel 5.x or the 10Gbit ports break due to a kernel-module issue.