But up until two or so years ago no one in any mainstream capacity was doing any antiagapic research at all.

which apparently has now become last five or six years. Does this represent an update of your views on the timeline?

The topic in question is fuzzy/indeterminite. The transition to widespread acceptance from marginalization was not instantaneous. The work currently ongoing began sometime after Resveratrol's antiagapic effects were discovered.

There were also minor items of research over the years which were conducted -- but senescence was, definitively, seen by the mainstream medical community as something to which only palliative care was worthy of researching, as opposed to senescence itself being a treatable condition.

Even that much is somewhat new historically speaking: there were no geriatricians in the US until 1978, for example.

But for example, work in trying to extend telomeres dates from the 1990s and the basic idea about telomeres dates from the 1970s. I don't know if this work gets classified if as "actual, honest" by you since it turned out to a large extent not to work as well as people thought it might.

No, its failure to that end has little to nothing to do with the topic at hand. It doesn't apply for the simple reason that the research in question was not done for the purpose of combating senescence. It was never meant as anything other than a tool for theoretical understanding of the role of telomeres in biology -- a topic we still understand only very poorly, with many conflicting ideas about the specific functions and purposes therein.

Also, in regards to the issue of premises, are you asserting that if scientists in 1900 or 1950 had put in current levels of attention into anti-aging that they would have succeeded at the level you estimate?

No. I have no such claim to make. They might have discovered something like resveratrol and ways to make it available to the common public -- that is, pharmaceutically mimic the caloric restriction effect -- and it's possible that if we extend this counterfactual scenario to the 80s'/90's, it's also possible that some other genetic therapies might have been uncovered/disseminated by now. (For example; work is currently ongoing at the SENS group to determine if senescent white blood cells can be screened from the body in a process similar to dialysis, which would allow the 'more vital' cells to repopulate within the patient, thereby restoring a more vital immune system, prolonging disease resistance in the elderly. This is also something that conceptually could have been in widespread application as early as the late 70's.)

There's an unstated premise about how much medical/biochem knowledge we have now.

No, there really isn't. It's not about that. It's about topical focus. It's about old age itself being seen as a topic worthy of being disassembled and its mechanisms researched in order to find solutions to that effect. The failure for this to have occurred until now is not representative of any promise of immediate success upon the conceptual breakthrough but rather a guarantee of the absence of success in the absence of the concept.

I'm reminded of a science fiction short story that delineates this same idea, in a way, though obviously with more "fantastic" results: Turtledove's "The Road Not Taken".