The thing I see people missing a lot in the discussion of "where the aliens at" is:

• you couldn't do complex chemistry until Population I stars formed, so there's a floor on when life appears
• the conditions for life might be rare
• life might be rare
• eukaryotic life might be really rare
• multicellular life could be even more rare
• complex multicellular life might not appear in the lifetime of the planet (we were mostly soup until the Cambrian explosion)
• Life tends to settle in local maxima. If there's no big reset like the mass extinctions of Earth, something in the intelligence local maxima might never appear
• speaking of, mass extinctions might be too rare to provide useful shuffles or too frequent to develop something in a similar niche as humans, or they might kill 100% of life instead of 95%
• back to local maxima: tool using requires a dummy amount of things to go right. Passing down tool use culturally requires even more things to go right
• there's no particular evolutionary guarantee for highly social, highly cooperative, intelligent, tool using, knowledge passing species to evolve
• even if there is, there's no drive to industrial revolution. Modern humans existed 250k years before we figured out agriculture
• and again, too much instability wipes out whatever progress you make. Humanity bottlenecked to less than 10k people at some point. What if we hadn't recovered?
• and once a species is technological, what ensures it won't blow itself up?
• ok, it's made it this far, and it turns out space can't be conquered, or the species simply doesn't have a wanderlust drive

And all this is against the fact that, cosmically speaking, the universe is really young and complex chemistry wasn't possible until somewhat recently because there wasn't enough of those elements. Maybe we're the first to get to this point.

There's no real reason for intelligent, technological species to occur.