That's simply not true. The retirement communities simply aren't why the water shortage is happening. It's agriculture, not residential use. The water usage numbers are well known. You're just assuming that population growth must have caused the water shortage, while ignoring the much greater increases in agricultural usage over the same timeframe.
The reason for the complaining is the population not the farmers. Why do you think they built the retirement communities in the desert? That's right! The land was gobsmackingly cheap! Why? Because the land was reeeeeeally shitty because the water sources were so poor! Would you be so defensive of the residents if this was Florida coast?
This is really quite simple: farmers use the vast majority of the water. Residential use is small in comparison. We're talking about water. Land use is only indirectly related. It's illogical on its face to say that the main problem is residential use when farming uses vastly more.