Allright lets say interstellar travel is possible. All of human technology occurs within 100,000 years, but a space faring civilization would have a huge jump start. So lets say 10,000 years maximum to get from entry to go somewhere else.
Second Earth could send a ship to Centuari-Proxima but also 10 or so other worlds (say all 10 stars within 10 light years), maximally it would take 10,000 years to get to each. So that means we quintruple number of worlds in say 10,000 years once we reach say 100,000 years from now. So that means doubling time is once every 30,000 years. In 100,000,000 we easily have occupied every single star that can be bridged by say 100 ly travel in the entire galaxy, though I am sure some stars would not be reached because of hazards.
Not only this, but our solar system would have been colonized many time by different routes here from that same single starting system and it would be currently occupied by a number of colony ships floating around in the sun.
So either we are really clueless about sentient life in our system, they are very stealthy, interstellar travel is really really hard or impossible, or we are the first in an evolution that will populate the galaxy. If that is the case we may never see life in other galaxies because the space-time frame only allows us to look backwards in intergalactic time.
Lets talk about risks.
Could we be the first life form in the universe to define the universe (something beyond the scope of the visible universe that contains all energy and matter). Not impossible as one sentient had to have been first, but in comoving space-time, the question becomes meaningless.
Could we be the first life form in the galaxy to reach this level of sentiency. Improbable, but not impossible. The premise is that our galaxy evolved from gas and has been progressing with the evolution of more complex matter (more heavier elements), in the progression there are points were life is impossible, then becomes very rare, then more common place, then tolerant of sentient life, then probable that sentient life will appear. A half-life for first sentient life. During that progression one life has to be the first sentient and we could be that life form. Space-time is also tolerant of multiple first, this is because "age" is a measure of the progression of time and is dependent on speed and proximity to the galactic center where things age less quickly.
So now, we have an 100,000 year interstellar ship, it reaches destination and it collects comets and asteroids, and builds colonies (easily less than 1000 years for each colony) after accumulating a certain number of 1000 colony ships each with its own specialized factories it then begins build the next interstellar travel ship, no need to landing on habitable planets, but habitable planets would be terriformed and colonized at convenience. For example planets around red stars that have finally exited the flare stage might have material from the oort belt brought in to make atmosphere, filtering the elements to add just th right amount of oxygen and hydrogen and nitrogen, then adding the right seeds (like cyanobacterium and other organisms to slowly build up life. Once you have 'bread crumb' colonies between Earth and 'terriform' planet you could transfer complex ecosystem inhabitants by cryogenic storage (egg or spores) that are then implanted into mechanized 'maternobots' that specifically provide the needs for each organism and bring species back to life on the new world. The sentients could build specialized command and control, invention centers etc on these worlds.
