Some tentative conclusions can be drawn from the information we have available.
It seems entirely plausible that life takes a long time to develop into complex multicellular forms; this took several billion years on Earth, and unless it took unusually long on our planet we might expect it to take a comparatively long time on another world.
Perhaps the average development time on other worlds is ten times as fast- perhaps it is ten times slower. If the average development time of complex multicellular life is ten times as fast, then complex biospheres may be common.
The length of time a planet occupies the habitable zone is also important- over time the habitable zone moves outward from the star, as the star heats up. In a billion years or so, our own planet will no longer be in the habitable zone as it is currently understood. Cooler K-class stars get warmer more slowly than our own star, but their habitable zone is much smaller. On the other hand hotter F-class stars have larger habitable zones, but get hotter more quickly, so the zone moves past a planet quite rapidly. I'd suspect that the best class of star for habitability concerns would be a slightly cooler, somewhat longer lived G-class star.
We can't tell much from the absence of radio detection, as numerous discussions on this forum seem to indicate; but some other indications seem to suggest that we are not imbedded in a galactic civilisation. I'd expect to see evidence of past alien exploration (no convincing evidence exists) or current alien presence; I'd also expect to see megastructures in at least some planetary systems, and perhaps emissions or waste heat from interstellar spacecraft or energy generation or collection. For example we can probably exclude the possibility of a civilisation using zero-point energy to generate power, as such a civilisation would probably emit more energy than the stars in the galaxy.
If life is abundant, it does not seem to have developed into a detectable civilisation anywhere near our star- a civilisation using large amounts of energy nearby would have been detected by now. But there might be untold numbers of civilisations with lower levels of energy use throughout our galaxy. One might wonder what prevents a hypothetical civilisation from developing into a detectable one. Are they deliberately hiding from each other?
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