I dont know, to me, you are posting the cycle of life. Your saying it isnt about young and old, well who is going to pay for the old?
Also the people you bring up who invested their lives for 20+ years, got the same deal as the generation before them, assuming your argument those people of 20+ years benefited from the generation before them much as you describe the new generation coming into the area now.
Also it cost a lot of money maintaining the old sewer systems, drainage systems, water systems as it does putting in new ones.
You can also bet your rear end that those new developments will be paying for the rest of their lives just as the older are paying now. So I am unsure of the debate. It cost money for government to run, everyone pays their share every year of their lives. They according to your post benefit when they are young but make up for it when they get older because they pay the same.
Your also leaving out a whole slew of others things, like sales tax income. The young are contributing more to local coffers because they spend more. It's all irrelevant to me. You live in an area, there is no protected group, young or old from paying their fair share even though seniors in MANY areas do get a small tax break, some high tax areas these breaks are so large that the young have a valid argument that they are supporting the old. Nassau County NY is one such area where young people pay 5 digit tax bills and older residents get 4 digit tax breaks.