Yeah, not having cake sqm is the one thing that will probably kill Opnsense as a choice for some people. That's not to say you cannot get excellent results with fq_codel, because you absolutely can (I actively use both OpenWRT and OPNSense on different network applications personally). It is definitely more work to get good results though. OPNSense's wireguard support has been excellent for a number of years now, and it's exclusively what I use for tunneling in a VPC I rent.

If you're particularly constricted on host hardware and need a lightweight router to manage multiple other VMs on said host, I could definitely see the benefits of running a minimal OpenWRT over OPNSense in that case.