Useful biotechnology may increase life expectancy in the near term, but not so differently as has been discussed here. We have basically zero chance of counteracting a life time of bioaccumulant toxins, telomere shortening, and numerous other shortcomings such that actual maximum lifespan sees a meaningful bump.
There are other organisms that do this, so there is no physical limit in this. It's just an engineering problem.
For example, telomere shortening is already being worked on. Look up Bioviva science, they have made first human experiments and results look very promising.
I think people just got used to being fatalist in this regard, because it is psychologically easier than to tackle this problem.
To me, it just seems like an (admittedly difficult) engineering problem that we're likely to make a lot of progress on. I'm currently studying biology and it's pretty amazing what humans have discovered in the last ~100 years about how the body works at the atomic level.
As a meta-point, I find it fascinating how nearly completely divergent our bayesian priors are (I think our chances of counteracting all of those forces you mentioned are, on a long enough timeline and assuming we're not destroyed and we have sufficient energy, greater than 90%).
