I see your points. Humans aren’t just one pot, it’s true. However, my fear is that with very scarce resources, you end up with an oligarchical system that stifles innovation. That’s always what happens. The rich get into power, and instead of using that wealth for research, they use it to maintain their position. The USA is on that track currently with middle class wage stagnation and the wealthy consolidating all the wealth over the past 30 years. Luckily, there’s still plenty to go around so there’s still lots of innovation, but once oil runs out and GW hits hard, there will be a lot less. You need an egalitarian political system to foster technological innovation, and with resource scarcity that goes out the window.

Once you’re at the point where recycling is cheaper than mining new resources, you’re a very poor country. Take Cuba, for example, which experiences artificially induced scarcity from the US embargo . Recycles everything, very poor, no innovation comes from there. Everyone is too busy trying to feed themselves. That would preclude interstellar travel.

Also, oil isn't the only necessary resource being depleted. We’re currently in the “bumpy plateau” phase for peak phosphorus, which is just as scary as peak oil, if not more so. Once we deplete that, we’ll have to turn to much more expensive organic farming to produce food, and we'll be back to the 1800s.

Any developing civilization will inevitably use EM radiation for communication, whether it be radio, microwave, laser, IR, whatever. There is nothing else to use, it’s cheap, it’s a fundamental of our universe, it’s ubiquitous, and it travels at the speed of light. It’s too tempting and obvious not to use, regardless if the life form is carbon based like here on earth, or silicon based breathing ammonia with copper-based blood cells. Even ocean based life will have to leave the ocean to accomplish interstellar travel, when they do, their initial communication will all be done via EM radio waves.

That being said, as I mentioned, radio is only detectable over very short distances (hundreds of light years), before the weak signals get lost in the background radiation. And only for a short window of hundreds or thousands of years before some other technology is discovered. So, very, very hard to detect.

As for fully exploiting the resources of their solar system before moving to other stars: I think these would occur concurrently. That’s the way we would do it, and it only makes sense. If you can, you will. Europeans explored and discovered the new world before cultivating every square inch of Europe. At the same time, they continued cultivating Europe while developing new colonies. Even if an alien civilization decided to fully exploit their current solar system before moving to another star, you’re only talking a few thousands of years difference, a blink of an eye for an interstellar civ that could have developed millions of years ago.

As I said in my previous post, it *appears* that FTL is possible, but until we achieve it we don’t know. In the 1800s people thought going to the moon might be possible in theory, but there were many, many hurdles to overcome before we got there.

So to sum up:
The Fermi Paradox is not a paradox at all. It is the natural state of things.

1. Life may be common, but intelligent is likely quite rare (see how long it took Earth to achieve it, for example).

2. Even if intelligent life is developed, the chance that it develops interstellar travel is quite rare. Such civilizations are likely to collapse or destroy themselves before developing and exploiting the ability.

3. Even if they do develop interstellar travel and exploit it, they could collapse/destroy themselves before reaching us.

4. If they do reach us, they will orders of magnitude more advanced than us both technologically and philosophically, and they will have some form of the Prime Directive in place. They would observe from a distance, but never reveal themselves for fear of disrupting our development.