DOORS is a legacy system developed in the previous century. It lacks Agility and due to its fragmented nature, it provides limited traceability on artifacts and subpar reporting capabilities. IBM CLM is not one product but rather a product suite with multiple separate components. The tool suite has a steep learning curve, and high installation, rollout, and operating costs.
DOORS Next Generation (which despite branding was originally not targeted at System Engineers but at IT people) has no fine granulated read access control within a project and no complex queries with groups. DOORS NG does not scale well for large projects with true horizontal autoscaling by means of clustering, which results in limited performance when outgrowing a single server for your project.