My first argument was that, in a hypothetical future world which had solved aging, it would be likely they would have also solved cancer, dementia, etc.
My second argument was that our current moment in time is not likely to be near the end of the possible tech tree, that large advances in technical knowledge and ability are very likely still in front of us, and that therefore it doesn't make sense to argue that if by now we haven't already solved [x,y] then we probably never will.
Your argument seems to be that we don't fully understand the unintended consequences of our inventions, and that there's a distinct possibility that some of those unintended consequences may cause us to go extinct before we get smart enough to stop making those kinds of errors.
I agree with that argument. I don't see any conflict between your point and my point - just between your point and some claim I didn't make about techno-utopia being just around the corner.
Some kind of "techno-utopia" does seem like a possible future, but not necessarily a probable one. I don't know if we'll make it there. We're not reasonable enough, maybe. And one of the ways in which we're unreasonable is that we tend to read into our opponents' arguments things they didn't say and impute to them beliefs we don't have evidence that they hold. That isn't helpful, and on the large scale it's distinctly harmful - it's a major part of the political polarization and divisiveness that is dragging down our collective ability to cooperate and come to reasonable compromises.