I think the point is that they would have colonised Earth already. It is comparing the age of the Earth (billions of years) to the size of the galaxy (100kly)
Maybe every advanced civilisation ends up turning inwards to simulations rather than outwards. Maybe there are aliens all around us, but we can't notice them, because we're living in someones phone, in the latest top-hit: SimHumans5000.
There's quite literally an infinite number of possibilities where we're not alone after all, and part of the problem is that we don't just not know the values to plug into the relevant probability calculations, but we don't even know all the variables.
For a civilization living for trillions upon trilions of years inside a simulation, intergalactic latancy is just a blink of an eye -- they have no reason not to distribute their simulation across the galaxy.
All of the burning stars would be just lost time for such a civilization
Not saying I believe this, but are we sure they haven’t? There’s a bunch of fringe people who believe it did happen.