The rarity and the eventual self-imposed and/or ecologically imposed frugality of advanced civilizations may help resolve the Fermi paradox.

Imagine that our civilization manages to work out its current predicaments and enters a new era of rising living standards and shrinking population. It is conceivable that within a couple of hundred years Earth's population may actually be less than its current number. What then? Exploration of space and colonization might be more feasible; however, modest incremental exploration of neighboring planetary systems rather than all out rampant colonization of every Earthlike planet is likely for a civilization that realized that downsizing consumption and taking care of ecosystems is the key to survival. Remember, the Fermi paradox has to be seen in its socioeconomic context-- it was concocted during a period of rapid economic growth and accelerating endless growth seemed like the natural path for our civilization. Now many thinkers are challenging the wisdom of the endless growth and consumption doctrine (for example, in the book "The Upside of Down" and "The Long Emergency") now seems more like a path to disaster. So, it seems likely that a civilization that comes to terms with the limits of growth may do so too late, or, if they realize the limits before catastrophe occurs and downsize as a result, then they are likely to apply this same frugal philosophy to the exploration of the cosmos (it did not work here, why do it out there?). This plus a small number of intelligent beings would help explain away the paradox. But, again, even here Fermi haunts us: all it takes is one galactic civilization that decided to engage in exponential explansion and we should be familiar with those folks by now.

Here are some hypothetical numbers:

Drake equation gives us a total of 10 intelligent planets in the Milky Way galaxy, for the sake of discussion. So, 4e11/10= 4e10 stars don't have an intelaligent planet for a every one that does. Question: How close (I know it must be more than a kilolight year) approximately would the nearest intelligent planet be?

5 of them fail to realize that they must live in harmony with themselves and their ecology and thus fail to achieve interstellar flight or do anything else grand as a result?

Out of the remaining 5, 3 achieve harmony but only explore their solar system and engage in modest colonization (akin to us putting a self-sustaining colony on Mars).

The last two achieve interstellar flight, but are satisfied with colonization of one or two other systems.

Thus, no civilizations engage in rampant exploration, period.