He did call them out. Other presidents before him did the same. The major difference between him and the other presidents: he’s the only one who made plans to abandon NATO.
The major difference was that past Presidents gave lip service to other countries meeting their obligations, but everyone knew it was empty rhetoric. That assumption was no longer valid with Trump.
You may continue to believe that he was intentionally trying to weaken NATO for whatever negative motive you want to assign, but objective truth is that his term ended with NATO being much better funded and with him publicly giving credit to those countries who upped their game and said the US was committed to NATO.
On the topic of the reported plans to pull out of NATO, maybe those were legit or maybe those were floated to apply pressure...IDK. However, I believe it's fair/rational to question continued participation in a Treaty in which the vast majority of participants are not holding up their end of the bargain (one being the 4th largest economy in the world).