Prime numbers are a consequential concept. Maybe that octopus knows about another consequential concept that we haven't been thinking about for many hundreds of years.
Also, maybe the smartest thing to do if an unknown entity tries to contact you, is to play dumb.
Sure, I mean intelligent life is interesting to us because it's novel. If there is other intelligent life in the galaxy (universe), it probably implies that intelligent life is relatively common. So, more (less) intelligent life would be extremely inconsequential to them. Why waste resources studying something already well understood?
My point is that intelligent life may have discovered something we don't know already, even if it's dumber than us.
I suspect that if life is common enough that we're boring to most other forms of intelligent life, we'd probably find at least one or two other species that are interested in us, and if it's rare enough that there's only one or two other species out there, then chances are we're interesting enough that some of their folks would want to visit us and find out our deal.
Obviously I think there's a point to us trying to communicate with whatever is out there, I just think we shouldn't be surprised by the lack of response.