I agree my post was too over-simplifying and over-generalizing.
Do you know how many of these are wireless / with high packet loss? So far I understood DDS as something that was (pre-ROS 2) run mostly in industrial applications over wired connections and usually with small(ish) packets. The baby problems ROS 2 DDS RMWs had when people started using them over Wifi would suggest that there is (was) a big problem with wireless transport and it took the DDS vendors a few years until they came with some kinds of solutions.
I think the DDS vendors speak for themselves. If the problems I mention were only user-generated / misconfiguration, the vendors would not come with the extras that try to mitigate the problems. The sole fact that they invested lots of effort into solving the problems is a good enough sign for me that the problems found by ROS community were real. See for example ROS 2 Easy Mode, Discovery Server and others.