> isn't telomeres a physical/chemical/biological reason we can't live forever?

It’s one component, but not the only reason [1].

Naked mole rats’ telomeres do “not shorten with age but rather showed a mild elongation” [2]. They are long lived, for rodents, and don’t degrade into balls of cancer [3]. They nevertheless age.

[1] https://en.m.wikipedia.org/wiki/Senescence#Theories_of_aging

[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC6651551/

[3] https://www.science.org/doi/10.1126/sciadv.abe0174

I believe the argument would go "there's no fundamental reason we can't fix telomeres".

We need ECC for DNA, I could probably use a deep scrub.

Isn't the reason cancer? Eventually the DNA copying errors add up.

There are a handful of animals, mammals even, that essentially don't get cancer (some/all large whales and naked mole rats IIRC). So that might be solvable other ways.

Nitpick, it is far less likely, but they can still get cancer.

Cancer is not fundamentally unsolvable (AFAIK?). This is a tough question to answer though. Can we prove cancer to be solvable without solving it?

You also fix the copying errors.