Erm. Sorta?
Much medicine is stressing your system in a way that you should survive, and some other form of life (cancer, bacteria, fungus) should not. I don’t think adding oxygen magically restores telomeres: if this happens at all, maybe it is because our cells with less telomeres have died so our average has improved.
You are right in the general sense - all life is complexity, and eventually yields to entropy. In the long term, thermodynamic always wins. Adding oxidiser probably kills stuff. But life is not long-term, and taking advantage of local conditions is what life does. So, for example, there was a proposal to make the atmospheres in hospital wards 40% oxygen. This might help patients recover, and and it would also help keep surfaces sterile. I can see that working.
I doubt oxygen makes you young again. I doubt thermodynamics would allow that. But the marketing case - go, spend your pension fund on a hyperbaric chamber before you get too gaga - that is clearly going to work, dammit.
