How would you handle criticism from a supervisor who never served, yet criticizes the military for not teaching communication or teamwork?

Sometimes you just let them be ignorant.
Also realize what this person thinks of communication or teamwork maybe vastly different from what the rest of the world thinks it is. Sometimes those people think that teamwork is people doing everything for them and communication is reading their mind. Sometimes what we believe to be one or the other is received differently.
All in: far too little information to know the context, so maybe let it ride

Not enough context to really understand the dynamic but.... Sometimes a supervisor's view of "teamwork" is you doing exactly what they say without question or comment. Likewise, their view of communication is you basically being a "yes man/woman" and never question anything they say.

If the situation is toxic enough, there are other employers out there from which to obtain a paycheck. THAT is also a form of communication....

Glad I never actually had a Manager of Supervisor of that sort whom apparently has no idea what two way communication or teamwork is. I Myself as a Manager in the civilian world have always found hiring people with Military backgrounds to have huge advantages with people Who not only could work as part of a team but be counted upon to complete all tasks because they knew they had to be done and didn't need to be pushed. The Management job becomes a lot easier in My experience with people with Military work experience Who can be counted on each and every time to complete any standing or newly assigned task, supervise and Manage others and get the job done.