As your summary seems to mainly pertain to Trump berating NATO (actually some individual members), these members, particularly Germany, were indeed guilty of long-term under contribution relative to their GDP's and far less than their pledged commitments, which put even more burden on the USA. Trump reminded them of this but I don't think he really wanted the USA to quit NATO. Look what's happening now that Putin has attacked Ukraine - those that have not done so already, are increasing their military spending.
NATO would have been far more capable already if all members had kept to the deal over time. Germany, by far the largest economy in Europe, will take years to be at the NATO member strength that it should be at today.