I refer to intelligent life not inhabiting every corner of the galaxy.

Colonizing any part of the Milky Way takes time, expense, and
resources, no matter what the culture is like - to say nothing of
the desire and will to do so in the first place. So they would need
a good reason and make sure they had a reasonable chance for
success before they went ahead and colonized a star system.

Non-mainstream stars would likely be undesirable places to settle,
as red and blue giant suns tend to die out in nasty ways in relatively
short timescales. We might find some ETI around those stellar types
on a science expedition, but they wouldn't want to stay.

Red and white dwarfs - They will last for ages beyond our yellow
dwarf Sol and make up a lot of the galaxy, but will they be the
best places to maintain a long-term colony? Of course as the
stars and galaxies start dying out in the distant eons, huddling
around red dwarfs for survival may not be an option by then.

I know there are a lot of other factors and conditions here, I am
just going on the assumption as so many others do that interstellar
colonizers will be some form of organic life. They won't want or be
able to occupy every corner of the Milky Way, but other forms of
intelligence may, unfettered by the needs and limitations of organic
beings.

Please read the paper by G. Landis I linked to earlier in this thread.