Overpopulation is not the main problem. Rather, it's the maldistribution of income that is the first part of the problem. The second part of the problem is that such a huge proportion of our labor force is wasted on the production of increasingly superfluous stuff.
Why is it wasted that way? Because billions in profits can be made by certain companies and individuals from the sale of all that stuff.
If by some means we could reorganize society in such a way that people had alternatives to participating in this huge orgy of wasted labor and resources, there would be far more people available to, say, build and maintain affordable housing for all, make cities beautiful and more functional, provide more and better education for one and all, and protect the environment and thereby our health. And if incomes were then to be distributed more equitably, say to the extent that it was in the late 1950s or 60s, people who now live in cramped quarters and "bad neighborhoods' would have the income that was required to rent or buy larger living quarters.
Yes this presumes they had all been afforded an education that was maximally beneficial to them and which prepared them for some kind of job that was sufficiently useful to society. But in the larger scheme of things, is that really a prohibitively large presumption or requirement?
Freedom from excessive labor and long work-hours
In a truly free society, of a kind just suggested, blessed by such advanced technology as ours is and would be, people would not then be compelled to work anymore than they really wanted to. Yet, as Elliot Sperber recently pointed out, even though the mechanization and automation of agricultural and industrial work has been developing for well over a century, it has not (since the advent of the 40-hr week after WWII) resulted in an overall reduction in work-hours, but rather an increase. But how could this be?
One would imagine, as Alfred Keynes and Bertrand Russell did, that a free society would employ these new technologies in a manner that would create _more_ free time, not less. Indeed, in the 1930s, people commonly supposed that the continuing mechanization/automation of production would lead to a three-day work week! And this was indeed the goal of the more critical factions of the labor movement -- not more jobs and ever more work, but the _elimination_ of long-hour jobs and excessive work, and the development of an ever more just and leisurely society!
Needless to say, this goal was not realized. Instead, for the past 60+ years, most people have been working steadily more hours.