I don't have a horse in this race, but from what I read this is the part that can be construed as "slinging mud". I've put some [read between the lines] comments in square brackets:

  "Unfortunately, a simple re-usable component is not how things are playing
   out. Docker [much to our dismay] now is building tools for launching cloud
   servers, systems for clustering, and a wide range of functions: building
   images, running images, uploading, downloading, and eventually even overlay
   networking, all compiled into one [big and nasty] monolithic binary running
   primarily as root [how insecure is that?] on your server. The standard
   container manifesto was removed [those flip-floppers!]. We should stop
   talking about Docker containers, and start talking about the Docker
   Platform [since we can focus attention on our efforts that way]. It is not
   becoming the simple composable building block we had envisioned [which puts
   our offerings at a disadvantage]."

  "We still believe in the original premise of containers that Docker
   introduced, so [unlike those silly Docker people] we are doing something
   about it."

Later on, they specifically say:

  "the Docker process model ... is fundamentally flawed"
  "We cannot in good faith continue to support Docker’s broken security model..."

All these may be valid criticisms, but even ignoring my potentially off-base annotations it's difficult to read their announcement as anything other than "Docker is broken and can't be fixed". It's reminiscent of political attack ads which focus on the shortcomings of your opponent rather than the strengths of your own platform.