I'd even be fine with people who are billionaires living forever, so long as they don't remain billionaires / don't fuck with politics / etc.
Fundamentally the problem with living forever goes beyond billionaires. People get stuck in their ways of thinking, the mindset of living forever is completely different. Why should I even listen to someone who only lives a mere 40 years? What is a suitable punishment for someone that lives forever? How does it change murder?
Philosophically, living forever may be corrupt by nature.
The only way to tear down tiers of society is for some of those tiers to literally die off.
Sure, if people get stuck in their ways forever. But what if they don't?
If we can solve longevity, we might also be able to "solve" brain plasticity, therapy, psychology, sociology, etc., such that people's beliefs will be more flexible and people's minds more open.
I think it is incorrect to assume that we would solve biology while all of the fields researching the health of the mind made little progress.
We shouldn't imagine the future as being like today, only different in a few key ways - this is the trap of sci-fi authors. The future will be different in more ways than we expect. We might well fix 'old people are stuck in their ways' before we fix longevity.
The best analogy for a positive outcome I can come up with is living within our means as a species. Leverage AI, leverage all the tools we have for production, but we have to find equalibrium with ourselves and the universe we live in.
I'll vote for the terminators and meteors if we insist on living beyond our means.