The article is saying that mostly-suburb cities are not sustainable. They cost more to build and maintain over the long term than the majority of cities can recoup in taxes. That has little to do with employees, they are mostly talking about straight-line capital costs to dig up the streets and install new sewer lines. Even worse is that many cities grew in a relatively small post-war boom so a lot of that infrastructure will need replacing at the same time.

Towns don't typically provide all of water, sewer, storm sewer, and other such services... they might provide water. They can also just dig up everyone's yard to replace what infrastructure they do have because things are more spread out (lost of "wasted" land between the house and road) and far fewer people are disrupted (that also means projects can be done at a slower pace). They also have a much sparser police and fire department, far fewer parks, etc.