A lot of things had to happen to bring us here.
The collision with Theia forming our moon for instance. That gave us a tilt, seasons, tides and a valuable factor in the evolution of life and ecosystems.
None of that is a requirement for life or 'civilization'. One could as easily argue that life managed to evolve despite these instabilities, and it is stability after all that tends to favor life, especially advanced life. We barely made it here on Earth, evolving civilization only near the end of our window. Took 5 billion years to get here from the earliest life, and yet in another billion it seems conditions here will not support multicellular life at all. That's cutting things pretty close.
Also size of the planet, distance from the sun, earth structure, elements water, avoiding asteroids, avoiding volcanos, requiring volcanos, life evolving with us but not killing us in the process.
Size matters little if at all. Water (and carbon) is wonderful for our kind of life, hence the need for a 'habitable zone', but that seems common enough that there is at least one other planet with liquid water on it just in our solar system. Avoiding asteroids is part of the stability thing.
There was a study a while back that suggested that the best conditions for intelligent civilizations to form in our galaxy occurred closer in to the center of the galaxy than we are, and when the galaxy was much younger.
Here I have my doubts, since the center of a galaxy, especially early on, tends towards very unstable conditions. Sure, life might take hold on some planet in a habitable zone, but with so many rocks to wipe things out, and so many large objects (passing stars and such) to disrupt stable orbits, planets simply are not likely to stay habitable for any length of time. It's way out here in the boondocks that stability is to be found, and more likely with a smaller star with a far longer lifetime than that of our sun.
We've also heard neither hide nor tail from them.
Let's suppose that we would notice, that we could detect a civilization by looking for radiation that would not otherwise be emitted, so we could say see them even in Andromeda if they were there. What are the odds that a civilization would be thus detected?
Nobody has mentioned the 'great filter', which is a frequent solution to the Fermi paradox. It says that a civilization like ours is fleeting, and pretty much ends when the non-renewable resources run out, or until we wipe each other out. Either way it happens in an amazingly short time, so not only do we have to look in the right direction to see them, but we have to look at exactly the right time, and the odds of doing that are pretty much nil.
Here's a picture of the universe:
We are at the 'here and now' point. Put this picture (a nice poster size one) on a wall. Throw a dart at it. That's the alien civilization. If the dart doesn't land exactly on the red line, we cannot see it. Only an enduring civilization would have a significantly extended worldline long enough to possibly cross the red line, and it appears that such enduring civilizations (certainly not our own) are exceedingly improbable. That's a good reason we don't see them. The dart throws are simply not on that red line, and we only see stuff that is.
