I don't quite understand your logic here? The big barrier(s) doesn't seem to be tool use, but rather 1) the formation of life itself, and then 2) the move from single-celled organisms to multicellular organisms (this took 2 billion years on earth, so is clearly a very difficult step).
> our existence now is so unlikely that it's possible that we actually are the first. Something has to be first.
When the OP said that ^ I took we to mean humans with technology, presuming the OP meant that we were somehow special. Basically I took it as him saying that we're first because we're lucky so my argument was:
> How are we lucky? Look at all the other intelligent lifeforms on Earth! Surely the lucky winners would have had some sort of fluke that made them one of the few with intelligent brains on their planet! This could have easily happened sooner on Earth!
If the OP meant that life itself was extraordinarily rare on any given celestial object then that is something I don't consider especially groundbreaking since its part of the Fermi Paradox formula in its basic form the precise value of which has been debated for years and I do not find convincing.
"the leap to exponential tool" - the current human leap to exponential resource consumption seems to be colliding with the limited and fragile structure of the earth (IE, CO2 pollution is pushing to catastrophic global warming). A fair number of decision makers seem to expect some tech fix to appear when every indication is it won't. My point is "getting to stars" would require technological progress in a situation where a species learns to curb an appetite for exponential growth, something human beings certainly haven't achieved.
If you want to argue the Drake equation on its own, that is cool, but it wasn't what I thought OP was talking about. My central argument is that if we are first that is pretty unlikely because we have 1000s of intelligent species and for us to be first of many on our own homeworld in addition to being first in the galaxy or beyond is much less likely.
That said, I could see an argument being made for combative intelligences coevolving increased intelligence and this being the counterpoint to my counterpoint. Though I don't buy it.
As for number two, it's hard to comprehend a response that is reasonable because our cognition may be part of the "disturbing reasons" right?
The theory I more and more think is probably right is that there is some major aspect of the universe that we get wrong. What is more likely, humans thinking they understand something when they don't or that no life form was able to spread amongst the stars in billions of years? I have plenty of lived examples of humans with false knowledge.
It's a sort of meta Drake equation. [Likelihood humans are not as wise as they think they are]*[rest of drake equation] and I think the drake equation, as stated, correctly leads to the term "Paradox" given the conventional understanding of science as communicated by scientists.