If you know Vmware suite of cloud products and their differences I can say that Openstack is pure IaaS like vCloud Director with ability to create instances, images, networks and routers - all virtualized infrstructure from scratch.
The purpose of MIQ is like of vRealize Automation is to create catalog of usable services with deployed complex applications. As vRA the MIQ have ability for integration with multiple IaaS platforms and have good integration with application deployment solutions (such Ansible). On vRealize Automation you should configure vRealize Orchestrator for automation purposes but MIQ have out of the box such automation engine and this engine, in most cases, is used to control the infrastructure.
OS currently have such features as Heat, Murano etc for catalog of services publication, but they is too complex for end users who’s whant “just give me ready working application”. If you need such thing for your job than you need some Cloud Management Platform solution and you should decide one of them
Catalog of services are more necessary for corporate enterprises where users need to get usable applications for their work and engineers need the solution for automating their job.
But for service providers the “Catalog of ready to use applications” is a good way to attract customers and gain competitiveness.
One of the strongest abilities of the Cloud management platform is the possibility of integration with other systems (backups, monitoring, billing). For pure IaaS you should develop such integration by self.