But isn't spending almost by definition more short term than investing as it means paying for a good or service? Investing is at least not a form of spending, it too is a way of saving imo.

Perhaps it would be more right to say that sometimes, spending can be the best thing you ever did when buying an inspiring or educational book that changes your life for the better and results in your wealth increasing. Or spending a bit more in order to eat healthier as an investment in your own productivity. Or buying something for someone in need who ends up paying you back many times over later. Many examples of how good spending can be better at increasing one's wealth long term than saving in the bank these days, that's for sure!