Yet another poor article that mistakes noise for reality. For example, Mirantis may be busy, but most of their revenue comes from services, not product sales. On their customer success page (https://www.mirantis.com/company/customer-successes/) they can only come up with three paying customers using the Mirantis product as of today. The Gartner criteria for inclusion is clear and it's likely that Mirantis doesn't qualify.
Add to that Redhat distancing themselves from Mirantis, and there being almost no real product value-add from Mirantis above and beyond a.n.other Openstack distribution, then I think there has to be some question about the long term viability for Mirantis as a product organisation (which is what the quadrant is all about).
The same also goes for most of the other openstack start-ups; a lack of customers paying for the product and a not yet proven product based business model.
You forget Gartner's raison d'etre. Gartner plays to the CIO to advise them on what products they can buy without getting sacked in 3 years time. Garner magic quadrants are not driven by innovation or startups, but by those products which are low risk.
There's no question that the Gartner Quadrants will favour a long established organisation with deep pockets and little innovation over a new startup with fantastic technology, lots of VC capital but few customers.
Gartner is about recommending VHS over Betamax.