What Trump wants out of NATO is the same thing that every US President has been whining about for decades, for the other nations in NATO to meet their defense obligation. This isn't a new issue, it has been an ongoing one for a while (from 2005:
Sharing-and Reducing-the Military Burden - FPIF)
They said it in private while he says it in public. They were polite about it while Trump gets child like glee in pointing it out that Europe is all talk and little action when it comes to defense spending.
- Previous presidents made the threat to curb US involvement in Europe but no one took them seriously. Very few people don't take Trump seriously when it comes to his willingness to pull back US forces from Europe.
Depends on you are defining the use of the word rhetoric. If you are using the classic definition of utilizing all available means of persuasion in any given situation to achieve a goal then I agree. If you are defining it as meaningless speech that he won't do then I absolutely disagree as he has already shown a willingness to pull US forces out of countries that don't want to hold up their end of the deal.
It isn't just for his base, the majority of Americans support the rest of NATO meeting their defense contributions and that has been true for decades. I have noticed that he mentions it less then he did before for the majority of NATO, primarily focusing on two nations that do not actually meet it, Spain and Canada.