Could someone explain the joke? I've been dabbling with learning robotics and I've been confused by how ROS and ROS2 both appear to be actively developed/used. Is ROS2 a slow-moving successor version (like Python 3 was) or a complete fork?
The other half of the joke is that ROS was never an operating system either.
But the rest are firmly downgrades all around. It's slower (rclpy is catastrophically bad), more demanding (CPU usage is through the roof to do DDS packet conversions), less reliable (the RMWs are a mess), less compatible (armhf is kill). The QoS might count as an improvement for edge cases where you need UDP for point clouds, but what it mostly does on a day to day basis is create a shit ton of failure cases where there's QoS incompatibility between topics and things just refuse to connect. It's lot more hassle for no real gain.
And yeah I forgot, there's the added annoying bit where you can't build custom messages/services with python packages, only ament_cmake can do it so you often need metapackages for no practical reason. And the whole deal with the default build mode being "copy all" so you need to rebuild every single time if you don't symlink, and even that often doesn't work. The defaults are all around impressively terrible, adding extra pitfalls in places where there were none in ROS 1.
You're right ROS2 isn't all round better than ROS so the transition will never happen fully.
FWIW I'm working on an actual replacement for ROS, I'll post it to ShowHN one day soonish :P