This discussion and the points raised remind me of the old discussions about the strategy regarding ROS2 development and its relation to ROS1, so for conetext and completness I would like to link to http://wiki.ros.org/sig/NextGenerationROS/StrategyReview, which summarizes some of the points, on also has pointers to some of the preceeding discussions. I am posting this without any personal valuation either way. While it does not necessarily paint a perfectly balanced picture, and some of the dicussions are maybe also obscurred by heated personal arguments, I still believe that there are some valid points contained.
I interpret it such that the main fear from people that have argued for a different strategy to develop ROS2 is that there will not be a viable (in terms of necessary maintenance effort) path for large-scale migration and coexistence of code bases in ROS1 and ROS2, and that the advance of ROS2 might lead to the biggest disruption of the ROS community yet, by effectivly splitting it up in 2 communities, those who go on to only use ROS2, and those, that are “stuck” with ROS1.
So I guess the community should hopefully come up with ways to make sure that this does not happen (where this thread is part of such an effort).